Static Friction:
Static friction is the force that resists the motion between two surfaces that are in contact with each other but not moving relative to each other. It acts parallel to the contact surface and prevents the movement of an object initially at rest.

Sliding Friction:
Sliding friction, also known as kinetic friction, is the force that opposes the motion between two surfaces that are in contact with each other and are moving relative to each other. It acts parallel to the contact surface and opposes the movement of an object that is already in motion.

Differences between Static and Sliding Friction:

1. Definition:
- Static friction: It is the force that prevents the initiation of motion between two surfaces in contact.
- Sliding friction: It is the force that opposes the motion of two surfaces that are already in motion.

2. Occurrence:
- Static friction: It occurs when an object is at rest and remains at rest despite an applied force.
- Sliding friction: It occurs when an object is already in motion and experiences resistance as it slides against another surface.

3. Force magnitude:
- Static friction: The magnitude of static friction can vary and is equal to or less than the force applied to initiate motion.
- Sliding friction: The magnitude of sliding friction is usually less than the force required to initiate motion and remains relatively constant.

4. Direction:
- Static friction: It acts in the opposite direction of the applied force, preventing the object from moving.
- Sliding friction: It acts in the opposite direction of the object's motion, resisting its movement.

5. Surface Conditions:
- Static friction: Static friction is influenced by the roughness and adhesion between the surfaces in contact.
- Sliding friction: Sliding friction is influenced by the nature of the surfaces and the presence of any lubricants.

6. Transition:
- Static friction: Static friction transitions into kinetic friction when the applied force exceeds the maximum static friction force.
- Sliding friction: Sliding friction remains constant as long as the object continues to slide at a constant speed.

In summary, static friction prevents the initiation of motion, while sliding friction opposes the motion of objects that are already in motion. The magnitude, direction, and occurrence of these frictional forces differ between static and sliding friction.