Comment on page
There is a delay between user observed price and actual trade price. Where first one is an observation of the current state of the market by the user and the other is price of the trade that the user did based on its initial observation.
To make sure that the used does not receive bad (worse than expected) price we will use slippage parameter that will protect the user. The user will provide price that he/she is willing to trade at and maximum deviation from that price (slippage). If the final price is outside of this deviation then the trade does not happen.