The document provides an overview of how ATMs work. It discusses the history of ATMs, beginning with the first one installed in 1967 in London. It describes the basic components and functions of an ATM, including how customers authenticate themselves using cards and PINs, how ATMs are connected to networks to allow withdrawals from other banks, and the basic process by which funds are withdrawn. It also covers reliability issues, security features, and innovations in ATM technology over time.