'Btw' = by the way In Internet slang 'atm' = at the moment Outside that 'ATM' means 'automated teller machine' or what we call a cash machine/cash point in the UK. It's where you can withdraw money from your bank account using your card.

Did you first try to use an Internet search?

I have never heard of ATM outside of a banking institution. It means Automatic Teller Machine and that is when anyone can take money out of an account with out going inside a bank. BTW means: By the way

"By the way" and "automated teller machine".