I listened to a poker podcast,and the commentator said the player to his right had a re-shove stack,but he is not worried because the player to his right doesn't know he has a re-shove stack?
What is a re-shove stack and what size is a re-shove stack?
if anyone can tell me that would be great.
Thanks in advance.

First let's go over what a shoving stack is.

A shoving stack is where you have a sufficient number of chips where if you choose to raise, your only meaningful raise size is all-in.

So, for example, CO opens for $4, BTN is sitting there with $22. Normal re-raise (aka 3bet) sizes tend to be ~3x opening raise, which in this case would be $12. But if BTN did that he'd only have $10 left which makes him pot-committed anyway. So BTN's only meaningful bet-sizing is all-in. (Note however he might not actually go all-in, but to all intents and purposes, if he raises, he is all-in).

A re-shoving stack is the same but when faced with the situation where someone has already shoved.

Example: MP opens for $4 (with $96 behind), CO raises to $12 (with $88 behind), BTN shoves all-in for $22. Action folds round to MP.

Now MP is in a difficult position: if he just calls here, CO could then re-shove. CO has a re-shoving stack. The same applies if CO had just called MP's opening raise.

Thanks SWIMRUN

A reshove stack is when you can shove over a raise and get a fold.

This can be as small as 8-10BBs against awful players.

Generally though you want 15-20BBs.

That's why MP should know about isolation play: if he wants to play with the guy that shoved, he's better shove too, to try to make CO fold. If he calls anyway... at least MP did everything he could.