what do players do if they need to get up during a match?

i was just wondering

They get up.

lol! i meant do they like, pause the clock? do they just ask and get up, using their time?

No, you can't pause your clock.

You only stop the clock when you're resigning or making a claim to the arbiter (like your opponent made an illegal move).

So if you need to use the bathroom or something, you usually make a move, write it down, then stand up and go while your opponent's clock is ticking. Your opponent may move right away (or soon after you leave) and so you'll just lose that time.

huh! i didn't know that! thanks!

Yes, Chebyshevv is correct.   You can never pause the clock, unless the arbiter or tournament director is resolving a dispute on your board.   Any breaks that you need to take are with the clock ticking.   Like Cebyshevv said, make a move, do what you have to do quickly and hope that your opponent doesn't move right away.   In the old 40/120 tournaments, I used to have time to take a bathroom break and refill my coffee in between moves.   I think they shortened the time controls to 40/90 or 30/90 for most classic tournaments though.

So, only one heart attack permitted. If you have two, you're pushing your luck.

I believe it was Philidor,  but it might have been Steinitz who declared that you should always use the rest room before the start of the round

well i'd agree with that statement!

When I don’t have the move I am strolling round most of the time. So either my clock is ticking or my opponent‘s. What‘s the fuzz about?

Rules: (notice difference venue/playing area!)

12.2 Players are not allowed to leave the ‘playing venue’ without permission from the arbiter. The playing venue is defined as the playing area, rest rooms, refreshment area, area set aside for smoking and other places as designated by the arbiter.
The player having the move is not allowed to leave the playing area without permission of the arbiter.