Ask vs Bid

Ask

An ask price (commonly known as just "ask") is the price that a seller states they will sell their stock or good for. A firm ask price is one that is non-negotiable and will not change. Ask price is also known as asking price, offer price or simply "offer".

An ask is countered by an bid price by the buyer.

Since in real world situations, the buyer and seller will likely haggle and negotiate prices, this results in a bid-ask spread.

Bid

A bid price (commonly known as just "bid") is the highest price that a potential buyer is offering to pay for a stock or good.

A bid is countered by an ask price by the seller.

Bid-Size

The bid size is the amount of shares / units of a stock or security that a buyer is willing to purchase from a seller at the bid price.

A seller can counter with an ask size and ask price.

Ask-Size

The ask size is the amount of shares / units of a stock or security that a seller is offering to a potential buyer at the ask price.

A buyer can similarly counter with a bid size and bid price.