Straight right or cross is a normal right hand, follows the jab

Overhand right, is stepping in with a right hand straight
If you slipped a jab to the inside, step in (opptional) and hit them with a right hand
You would put alot of power in this as the opponent is not very likely to block the punch (left hand is out),and you have an opening
Noit used very often
Risky slipping inside a jab