When two things overlap, they are partly on top of each other.
Overlapping can be good, like when two friends' interests overlap, or bad, like when two jobs overlap and cause problems.
Examples:
The two blankets overlap on the bed.
Our schedules overlap, so we can't play together.
When I draw two circles, they overlap in the middle.
The two teams' practice times overlap, so they have to share the field.
Her story overlaps with mine in many ways.
The two pictures overlap, making a new picture.