[NSFW] How does a laxative do what it does?

Now, I know that laxatives basically make you poop more than normal, but how exactly do they cause that to happen?

I’m wondering because I bought some “slimming tea” a few weeks ago. I just had my second cup of it today and decided to do a little research on the active ingredients in the tea. The main herb in it is something called Garcinia and after a bit of research, I found that it is a laxative.

I’m a little reticent to keep putting something in my body if I don’t know exactly what it does, so naturally, I turn to the collective. How exactly does laxative do its thing?