The other relevant detail to consider when approaching swaps with the UNIWSWAP protocol is slippage. Slippage is the term we use to describe alterations to a given price that could occur while a submitted transaction is pending.
When transactions are submitted to ETHW, their order of execution is established by the amount of "gas" offered as a fee for executing each transaction. The higher the fee offered, the faster the transaction is executed. The transactions with a lower gas fee will remain pending for an indeterminate amount of time. During this time, the price environment in which the transaction will eventually be executed will change, as other swaps will be taking place.
Slippage tolerances establish a margin of change acceptable to the user beyond price impact. As long as the execution price is within the slippage range, e.g., %1, the transaction will be executed. If the execution price ends up outside of the accepted slippage range, the transaction will fail, and the swap will not occur.
A comparable situation in a traditional market would be a market-buy order executed after a delay. One can know the expected price of a market-buy order when submitted, but much can change in the time between submission and execution.