Call vs. Continuous Markets

Two typical structures of a securities exchange:

Call Markets
Where a stock can only trade at a specific time. Bids for the stock are collected and then traded at a specific time and at one price. It is typically only used for smaller markets.

Continuous Markets
Where a stock can trade at any time as long as the market is open. Buyers and sellers are matched up on a continuous basis and the price is determined through an auction or through bid-ask quotes.