Bid is a price by which you can sell currency being the first in a pair (XXX) and buy corresponding amount of currency being the second one in a pair (YYY).

Spread is a difference between Ask and Bid.

• The price that the market participants are willing to pay. A motion to buy a futures or options contract at a specified price. Opposite of offer. (Also see ‘Ask’.)
• The price that the market participants are willing to pay. Opposite of offer.
• The quoted price where a customer can sell a currency pair. Also known as the ‘bid price’ or ‘bid rate.’