Generally, orders are broken out into three main types - market, limit, and stop orders. All other order types are variations of these three.
Market orders have no trade price, they are entered 'at the market' and are filled at the best possible price available in the market.
Market order rules vary by the exchange as each has separate ways of maintaining orderly markets.
Limit orders allow the buyer to define the maximum purchase price and sellers to define the minimum sale price for the order.
Limit orders can be filled better, but cannot be filled worse than the limit price.
Stop orders do not immediately enter the order book, but must be triggered by a trade in the market at the price level of the submitted stop order.
Stop limit orders enter the market at the limit price level submitted with the order, while stop market orders enter the market as a market order once the stop price level has been triggered.
For example, if a crude oil stop limit order is entered with a stop price of 75.00 and a limit price of 73.00, the order will enter the market as a limit order at 73.00 only after the 75.00 price level trades.
If the order is entered as a 75.00 stop market order, the order will enter the market as a market order after the 75.00 price level trades.
Time Limit orders are specific modifiers attached to Market, Limit, or Stop orders. By default, orders entered are usually only good for the day or the trading session they were entered in, but adding a modified like 'Good Til Cancel' or 'Good Til Day' enables the order to remain active until it is filled, the trader cancels the order, or the parameters cancel the order.
Time Limit orders are specific to the trading platform and exchange.