Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: Normally a pawn moves by advancing a single square, but the first time each pawn is moved from its initial position, it has the option to advance two squares.

Pawns normally can only move by one square but the first move can be by two squares.