A Bitcoin ATM is a machine that buys or sells bitcoins for cash. It works almost like the ATMs you use today.
Using Bitcoin ATMs you can buy bitcoins with cash ONLY.
The average ATM charges a fee of 5-10%, but this is what people are willing to pay to buy bitcoins privately and with no verification.
There are many Bitcoin ATM manufacturates, so each ATM is different. Some require verification, although most don’t.