Bid-Ask Spread
The bid-ask spread in a market is the difference between the highest price a buyer is willing to pay (the bid) and the lowest price a seller is willing to accept (the ask) for an asset.
For example, if a stock's bid is $100 and its ask is $101, the bid-ask spread is $1.
Slippage
Slippage happens when the final execution price of a trade is different from the expected price at the time you placed the order. This happens when you place a market order, which tells the exchange that you want to trade immediately at the market price [→].
In this case, the execution price may differ from the price you initially saw if the market price changes between the moment you place the order and the moment it is filled.
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