Update : Aug. 29, 2003
Basically there are two kinds of order available on the TSE equities market, 'limit' and 'market' orders.
Limit orders are orders at specific prices, meaning that investors have stated that they want to sell/buy at a specific price or better. In other words a limit order represents the lowest/highest price that the investor is willing to sell/buy at. Limit orders offer investors the reassurance that they won't find themselves selling/buying at an unexpected low/high price.
Consequently though, limit orders can only be executed when there are orders matching the specific price requirements, which means there is a relatively high probability that they won't be executed. Also, limit orders tend to be inferior to market orders in terms of price.
Market orders don't indicate specific prices, but are executed at the best available price on the market at the time. They take precedence over limit orders, so they may be executed more easily than limit orders. This is a key merit for investors who need speedy transactions.
However, because investors do not put any price conditions on their orders, it is possible that they might end up with undesirable prices during periods of market instability. Thus it is very important that investors give careful consideration when placing market orders.