There are several kinds -
Corporate or career coaches, who support you in your career if you don't have a mentor already in your industry. So a sounding board if you're in a tricky situation at work, or you want to change job or career.
Then there are business coaches who support you if you are running a business of your OWN, and don't have a mentor already - it might be someone more like a counsellor helping you stay on track, or it might be someone who has already had success in your particular industry. So If you are starting a HR company, it could be useful to work with someone who has 25 years of experience in HR to bounce ideas off, talk through your worries etc, maybe get a few introductions.
When people look at successful people and say "Huh - it's all about who you know, isn't it?" - well, this is something that you can pay for. When I started my own business I WISH business coaches had been around then, or I had known about them. It would have been brilliant, because I felt very on my own and made some stupid mistakes.
OR it might be someone with a particular skillset to train you in - so instead of paying someone else to write all your sales material and email sequences, or you might benefit from a sales coach who will teach YOU how to do all that stuff for yourself, and how to not freeze on a sales call etc.
Inevitably there are lots of woolly coaches around, and people training woolly coaches to be woollly coaches, so there is def. an MLM element, but you wouldn't say the entire beauty industry is a scam because of Yoonique, right?