Priority

In stock markets, when there are multiple orders competing for a stock at the same price, a ‘priority’ determines when one of these orders will be filled or executed before others, at that price.
‘Priority’ is based on the time at which the order is received in the system. Although the electronic trading systems now execute orders at a very quick rate, still the process used is FIFO (First In First Out), which means that the order received first will be executed first, or it wil be the ‘priority’ order.

Priority Explained

Generally, the markets worldover operate on the basis of Price/Time priority. This means that orders are executed on the basis of best price and if multiple orders are received at the same price, an order entered into the system with an earlier time trades first.