Difference between congerving and diverging lens.
Difference between concave and convex lens.

Converging lens is able to form real and virtual image while diverging lens only forms virtual image.

Image may may be Large or small by converging lens while diverging lens forms small image.

Convex les is a converging lens which is able to collect light ray at a point.

Concave lens is diverging lens.
Used to spread light from a point.