Conservative force- A force is said to be conservative if the work done by the force depends only on initial and final positions of the body and not on the path taken.

The work done by a conservative force during a round trip of a system is always zero.

eg. spring force, gravitational force.

Non-conservative force- A force is said to be non-conservative if the work done by the force between two given positions of the body depends upon the path taken by the body.

For a round trip work done by the non-conservative force is non-zero.

eg. Frictional force.