Amazon seller glossary.

BFarm's Amazon seller glossary defines 21 core terms Amazon sellers encounter on Amazon: ACoS / TACoS / ROAS (advertising metrics), FBA / FBM / FNSKU / ASIN (operations), A10 / COSMO / Rufus / Amazon SEO (ranking and discovery), A+ Content / Brand Story / Brand Registry (listing and brand tools), Sponsored Products / Brands / Display / DSP (advertising formats), Pan-EU FBA / EFN (fulfillment networks). Each term is grouped by area and cross-linked to related terms.

Definitions written for operators who need clarity, not marketing fluff. Grouped by PPC, SEO, Listing, Operations.

Use these as a reference when reading Academy posts or evaluating Amazon agencies that throw acronyms without context.

ACoS — Advertising Cost of Sales
TACoS — Total Advertising Cost of Sales
ROAS — Return on Ad Spend
FBA — Fulfillment by Amazon
FBM — Fulfillment by Merchant
ASIN — Amazon Standard Identification Number
FNSKU — Fulfillment Network Stock Keeping Unit
A10 Algorithm — Amazon A10 Search Algorithm

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ACoS — Advertising Cost of Sales: ACoS is ad spend divided by attributed sales, expressed as a percentage. An ACoS of 30% means $0.30 of ad cost was incurred for every $1.00 of sales attributed to ads. Used to benchmark advertising efficiency against product margin.
TACoS — Total Advertising Cost of Sales: TACoS is total ad spend divided by total sales (ads + organic), expressed as a percentage. Healthier brands typically see TACoS decline as ads drive organic momentum, while ACoS stays in target. Watch the trend, not the daily number.
ROAS — Return on Ad Spend: ROAS is sales divided by ad spend — the inverse of ACoS expressed as a multiple. A ROAS of 4.0 equals an ACoS of 25%. Use ROAS when comparing Amazon ads to other channels in growth conversations; use ACoS when thinking in margin terms.
FBA — Fulfillment by Amazon: FBA is the Amazon logistics service where sellers ship inventory to Amazon fulfillment centers and Amazon picks, packs, and ships orders to buyers. Enables Prime eligibility, customer-service handling, and pan-marketplace coverage in exchange for storage and pick-pack fees.
FBM — Fulfillment by Merchant: FBM means the seller fulfills orders directly instead of using FBA. Useful for oversized items, slow movers, or brands with existing 3PL infrastructure. Loses Prime eligibility unless enrolled in Seller Fulfilled Prime (SFP).
ASIN — Amazon Standard Identification Number: ASIN is Amazon's unique 10-character alphanumeric identifier for each catalog item. Every product variation has its own ASIN. Used in PPC targeting, listing references, and account-level catalog management.
FNSKU — Fulfillment Network Stock Keeping Unit: FNSKU is the unique barcode Amazon assigns to each FBA inventory item, distinct from the manufacturer UPC. FBA-bound inventory must be labeled with FNSKU stickers (or use the Amazon Stickerless commingled program, rarely recommended).
A10 Algorithm — Amazon A10 Search Algorithm: "A10" is the informal name the Amazon SEO community uses for Amazon's current search and ranking algorithm, succeeding "A9" — Amazon does not officially confirm algorithm names or version numbers. It's understood to weigh sales velocity, conversion rate, organic vs. paid traffic balance, click-through rate, and review volume. Increasingly augmented by COSMO for context-aware ranking in 2024+.
COSMO — Amazon COSMO algorithm: COSMO is Amazon's context-aware ranking model that augments A10 with intent inference, listing extractability, cross-product context, and trust signals (review velocity, account health). Listings written for keyword density alone perform worse under COSMO than listings written in clear natural language.
Rufus — Amazon Rufus AI shopping assistant: Rufus is Amazon's generative AI shopping assistant launched in 2024, handling product discovery questions inside the Amazon app and website. As of 2025, Rufus answers ~270M daily queries. Listings that read like clear natural language with explicit benefits and use cases surface better in Rufus answers than keyword-stuffed copy.
A+ Content — A+ Content (formerly Enhanced Brand Content / EBC): A+ Content is the visual + narrative section below the listing description, available to Brand Registered sellers. Includes lifestyle imagery, comparison tables, brand story, and feature callouts. Improves conversion when designed for the buyer's top 3 doubts in the category, not generic decoration.
Brand Story — Brand Story carousel: Brand Story is the cross-listing horizontal carousel above A+ Content for Brand Registered sellers. Shows 4-6 ASINs from the same brand for cross-sell discovery. Useful when the brand has cohesive multi-product narrative; less impactful for single-product brands.
Brand Registry — Amazon Brand Registry: Amazon Brand Registry is the program that gives trademark holders elevated tools: A+ Content, Brand Story, Sponsored Brands ads, Brand Analytics search-term reports, and IP enforcement against hijackers. Requires registered trademark in the marketplace country.
Sponsored Products — Amazon Sponsored Products ads: Sponsored Products is the auction-based PPC ad format that promotes individual ASINs in search results and product detail pages. Most accounts spend the largest share of ad budget here. Available to all Professional sellers; no Brand Registry required.
Sponsored Brands — Amazon Sponsored Brands ads: Sponsored Brands is the headline-banner ad format above search results, promoting up to 3 ASINs with custom headline and brand logo. Brand Registry required. Typically 1.4× higher conversion than Sponsored Products on the same query when above the fold.
Sponsored Display — Amazon Sponsored Display ads: Sponsored Display is the audience-targeted ad format running on Amazon detail pages and (via off-Amazon partners) external sites. Used for retargeting cart-abandoners, defending branded keywords on competitors' detail pages, and audience-based reach.
Amazon DSP — Amazon Demand-Side Platform: Amazon DSP is the programmatic ad-buying platform for display and video inventory across Amazon-owned (e.g. Twitch, IMDb, Fire TV) and third-party properties. Distinct from Sponsored Display: DSP requires higher budgets ($30K+/month typical minimum) and managed-service or self-service activation. Priced and bought differently from auction-based PPC — CPM/programmatic buying, not pay-per-click.
PPC — Pay-Per-Click advertising: PPC means advertisers pay only when a shopper clicks an ad. Amazon advertising (Sponsored Products, Brands, Display) is auction-based PPC. Bid management, negative keywords, search-term mining, and KPI-window discipline are the core levers of PPC efficiency.
Amazon SEO — Amazon Search Engine Optimization: Amazon SEO is the practice of improving organic visibility and ranking inside Amazon search. Distinct from Google SEO: focuses on title structure, bullet keywords, backend search terms, A+ Content keyword indexing, and conversion-rate signals A10/COSMO weight in ranking.
Pan-EU FBA — Pan-European Fulfillment by Amazon: Pan-EU FBA is the Amazon program that distributes inventory across multiple EU fulfillment centers (DE, FR, IT, ES, PL, CZ) for faster delivery and reduced cross-border fees. Requires VAT registration in each storage country. Alternative is European Fulfillment Network (EFN) — single-country storage with cross-border shipping.
EFN — European Fulfillment Network: EFN stores FBA inventory in one EU country and ships cross-border to buyers in other EU countries. Lower compliance overhead than Pan-EU FBA (only one VAT registration needed) but higher per-unit fulfillment fees and slower delivery. Often the right choice for low-velocity SKUs.