A coulomb is a unit of electric charge in the International System of Units (SI). It is defined as the amount of charge transported by a constant current of one ampere in one second. This means that if one ampere of current flows for one second, it will transfer one coulomb of charge. Coulombs are essential for understanding electricity and are used in various applications, such as calculating the amount of charge in batteries and capacitors. The symbol for coulomb is C, and it helps quantify how much electric charge is involved in electrical circuits and phenomena.