I need to know for my game. For example, doing stop this script, what does that do?

A script is a stack of Scratch blocks. If you run the Stop this Script block - there will be no more processing of any blocks below that one.in that stack of blocks.

It will stop only that script, but the other scripts will still run. If you want to stop everything, use this block:

MizoFlash wrote:

-snipped for spamming-

That's both spamming and blockspamming. More information on spam.