How do cleanses work?

Chris_bee05

I keep hearing about people doing a cleanse or juicing etc.? How does stuff like that work? What exactly does it do? Does it actually help you lose fat or do you just lose water weight? I'm not trying to be rude or offend anyone, but I'm literally curious. Are cleanses and juicing similar? Do they do basically the same things or are they different? What are the benefits of a cleanse, who should do it, and how often?