In spot Forex, a pip is the usual smallest quoted move on a pair. For most majors it is the fourth decimal place; for yen pairs it is often the second. Brokers may also quote fractional pips, sometimes called pipettes.
Why care? Your profit or loss in account currency links pip distance, contract size, and lot size. Before you place a trade, knowing how many pips you are risking versus your stop helps you size the position instead of guessing.
This article is for education only. It is not investment advice. Always check your platform specification sheet because pip definitions can vary slightly by instrument.