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: This arises when a pawn uses its initial-move option to advance two squares instead of one, and in so doing passes over a square that is attacked by an enemy pawn.

This happens when a pawn uses its initial-move option to move ahead two squares instead of one square. During this move, the pawn passes over a square that is attacked by an enemy pawn.