What distinguishes a tourbillon from a standard escapement?

A tourbillon is specifically designed to improve timekeeping accuracy by addressing the detrimental effects of gravity on a watch's movement. In a standard escapement, the balance wheel's position is fixed, which can lead to variations in timekeeping based on the orientation of the watch. In contrast, a tourbillon places the escapement and balance wheel in a rotating cage, allowing it to continuously change its position. This motion averages out any positional errors caused by gravity, leading to more accurate timekeeping, particularly in mechanical watches.

The other options do not accurately represent characteristics of a tourbillon. For example, a tourbillon still requires power to function, it does not incorporate a unique winding mechanism that distinguishes it from other types, and it does not improve water resistance. Its primary function is indeed centered around enhancing the precision of timekeeping under the influence of gravity.