What characterizes transform faults?

Transform faults are characterized by the movement of tectonic plates that slide past one another horizontally. This lateral sliding motion is a key feature of transform boundaries and is responsible for the occurrence of earthquakes. As the plates move past each other, friction can build up along the fault line, and when the stress exceeds the strength of the rocks, it is released in the form of seismic energy, resulting in earthquakes.

The process at transform faults differs from divergent boundaries, where plates pull apart, and from convergent boundaries, where plates move towards each other, often resulting in vertical movement. Therefore, the horizontal sliding motion of plates is the defining characteristic of transform faults, making this the correct answer.