What is matched betting?

[Zofloramummy]

I’ve noticed on a few threads MN’s saying that they are making money from matches betting. What is it exactly and is it worth it?

Single parent, low income and on UC. I work full time and I’m basically looking for any legitimate ways I can boost my income that doesn’t require me spending a fortune on childcare or a large outlay.

I've tentatively started this a few times but as much as I know it's safe, I worry I will make a silly mistake ie wrong decimal place or something. Also, can it affect credit rating?