A bitcoin ATM is an internet machine that allows a person to exchange bitcoins and cash. Bitcoin ATMs offer bi-directional functionality enabling both the purchase of Bitcoin as well as the redemption of Bitcoin for cash. In some cases, Bitcoin ATM providers require users to have an existing account to transact on the machine.
Bitcoin machines are not ATMs in the traditional sense and probably use the wording ATM as a neologism. Bitcoin kiosks are machines which are connected to the Internet, allowing the insertion of cash in exchange for bitcoins given as a paper receipt or by moving money to a public key on the blockchain. They look like traditional ATMs, but Bitcoin kiosks do not connect to a bank account and instead connect the user directly to a Bitcoin exchange.