Amazon Seller Jargon, Decoded: The Core Terms Every New Seller Needs

Selling on Amazon and Walmart comes with its own dialect, and most of it arrives as acronyms thrown around as if everyone was born knowing them. The problem isn't that the jargon is hard — it's that misreading a single term can cost you real money. Confuse a fee for a margin, or misjudge what a ranking number means, and you'll buy the wrong inventory or price a product into a loss. This is a plain-English glossary of the terms that actually move your profit, grouped by what they affect, so you can read a listing, a report, or a sourcing tool and know exactly what you're looking at.

Terms about the product and the listing

• ASIN — Amazon Standard Identification Number, the unique code for every product on Amazon. It's how you reference, search, and track a specific listing.
• SKU — Stock Keeping Unit, your own internal code for a product. The ASIN is Amazon's identifier; the SKU is yours.
• Buy Box — the Add to Cart button on a listing shared by multiple sellers. Winning it is most of the sale; losing it sends buyers to "other sellers" and your conversion craters.
• Listing — the product detail page itself. On a shared listing, many sellers compete for the same Buy Box.
• Gating / ungating — whether a brand or category is restricted. "Gated" means you need approval to sell; "ungating" is the process of getting it.

Terms about demand and ranking

• BSR — Best Sellers Rank, a number showing how a product ranks by sales within its category. A lower number means it sells more. It's a proxy for demand, not a precise unit count, so read it as a signal of relative velocity.
• Velocity — how fast a product sells, usually expressed as units per day or per month. It tells you how quickly your cash comes back after a buy.
• Conversion rate — the share of people who view a listing and actually buy. Higher conversion means your traffic is working harder.
• Organic vs. paid — "organic" sales come from natural search ranking; "paid" sales come from advertising you pay for per click.

Terms about fulfillment

• FBA — Fulfillment by Amazon. You ship inventory to Amazon's warehouses; they store, pack, and ship orders and handle most customer service. You pay storage and per-unit fulfillment fees in exchange.
• FBM — Fulfillment by Merchant. You store and ship orders yourself. More work, but you keep control of shipping cost — often the better model for heavy or slow-moving items.
• WFS — Walmart Fulfillment Services, Walmart's equivalent of FBA for sellers on its marketplace.
• 3PL — Third-Party Logistics, an outside warehouse that stores and ships your products, often used to prep and feed inventory into FBA or fulfill FBM orders.

Terms about money and advertising

• Referral fee — the commission the marketplace takes on each sale, typically around 15% in most categories. It comes off the top of every order.
• Landed cost — the all-in cost to get a unit ready to sell: product cost plus shipping, duties, and prep. Your true profit is what's left after landed cost and all fees.
• Net margin — profit as a percentage of the sale price after every cost. This is the number that tells you whether a product is actually worth selling.
• ACoS — Advertising Cost of Sales, your ad spend divided by the sales those ads generated. Lower means more efficient advertising.
• TACoS — Total Advertising Cost of Sales, ad spend as a percentage of total sales (organic plus paid). It shows how dependent your whole business is on advertising.

Two distinctions trip up new sellers constantly. First, BSR is a ranking, not a sales figure — a lower number is better, and it only tells you relative position within a category. Second, the referral fee and your landed cost are different things, and your real profit only appears after you subtract both. Get those two straight and most of the rest follows.

Frequently asked questions

What's the difference between ASIN and SKU?

An ASIN is Amazon's universal identifier for a product — every listing has one, and it's shared by all sellers on that listing. A SKU is your own private code for tracking your inventory. You use the ASIN to find a product on Amazon and your SKU to manage it in your own records.

Does a high BSR mean a product sells well?

It's the opposite — a lower BSR number means more sales. Best Sellers Rank orders products by sales velocity within a category, so #100 sells more than #10,000. Treat it as a relative demand signal, not an exact unit count, since the same rank means very different volumes in different categories.

What's the difference between ACoS and TACoS?

ACoS measures ad spend against only the sales those ads produced, so it tells you how efficient a campaign is. TACoS measures ad spend against your total sales, organic plus paid, so it shows how reliant your overall business is on advertising. Falling TACoS over time usually means your organic sales are growing healthily.