Question

difference between self-confidence and over-confidence

Answer 1

self confidence is trust of a person which he has on himself
over confidence is doing of work with lack of self confidence 

Answer 2

Confidence is an internal feeling of trust and joy.
Over confidence is an external display of superiority only.

Confidence leads to paths which has success and appreciation.
Overconfidence avoid right path leads to paths which has failed.

Confidence: I can do it.
Overconfidence: Only I can do it.