Order book

Each market has a Yes and No order book, with separate Bids (buy orders) and Asks (sell orders):

For example, in the market concerning the Valentine's Day BTC price, traders are offering to sell “Yes” shares at 51 cents, the price you’d pay if you placed a Market Order to buy. Conversely, traders are bidding 49 cents to buy “Yes” shares - the amount you’d receive if you placed a Market Order to sell.

The difference between them is the Spread, and the lower the better. Placing market and limit orders is the method for buying and selling shares using the order book.