What is an unbank Bitcoin Teller Machine (ATM)?

Could you elaborate on what an unbanked Bitcoin Teller Machine (ATM) entails? I'm curious about how it differs from traditional ATMs and how it caters specifically to those without traditional banking access. Does it provide a means for individuals without bank accounts to transact in Bitcoin, and if so, how does the process work? Are there any additional considerations or challenges that arise with this type of ATM, and what are the benefits for those utilizing it? I'd appreciate a concise yet comprehensive explanation of the concept and its implications.