An underhand serve in volleyball is when u hold the wall with your (non writing hand) and then you hit it out of your hand (WITHOUT TOSSING IT) with your (writing) hand.
underhand serve hit spike jump serve
You should hit it with an underhand pass, otherwise known as a bump.
Underhand is where your hit the ball by reaching forward underneath it. Overhand is where you hit the ball above your head. Which one you use would have to depend on where you are relative to the ball. If it is above your head, you will have to use overhand (maybe you will have to jump), while if the ball is going to hit the ground in front of you, you will have to use the underhand hit (and you may have to dive for it).
only for younger players
Underhand, Side and Spike
use your fist
pass hit block spike set dig jump serve underhand serve
when serving the ball underhand, you want to form a fist with your dominate hand and hit the ball at the wrist which provides you with the best combination of control and power
over-hand and underhand