Final answer:
Slickensides are the grooves cut parallel to the fault movement direction. They provide geological clues to the history of fault movements and the stress regime.
Step-by-step explanation:
The grooves cut into a fault surface parallel to the movement direction are called slickensides. These features are formed as a result of friction when the blocks on either side of a fault, known as the footwall and hanging wall, slide past each other. Faults can be categorized into different types, including normal faults, reverse faults, thrust faults, and strike-slip faults, depending on the nature of the displacement between the blocks. The presence of slickensides provides insight into past fault movements and can help geologists determine the type of stress regime that was active during the fault's history.