Main characteristics of ATM
ATM is a connection-oriented technique  ó information in form of cells is routed through the network along a single path. Cells are always received in sequence.  
Statistical multiplexing of cells.
An ATM connection is by definition unidirectional.
ATM supports higher layer service adaptation, and may support different degrees of Quality of Service (QoS) and traffic management (IP term: traffic engineering).
virtual connections