ATM: Asynchronous Transfer Mode
Mostly used for maximizing network resources by segmenting and prioritising traffic and efficiently distributing bandwidth. This protoccol offers built-in QOS features and is primarily found in telecommunications, healthcare networking and media processing.

ATM Definition from Webpedia


Frame Relay

Less expensive, but slower, than ATM and used mostly for telecommunications (WANs).

Frame Relay definition from Webpedia

Hope this helps.