What is the difference between ISA Server and UAG?

For several years Microsoft sold the ISA Server that provided many network related features. Most used was probably the feature to publish web pages on to the Internet, as SPSS, MOSS and OWA whitepapers recommended you to put an ISA Server in front of the web server.

Microsoft now released a new version, and divided the ISA Server into two ForeFront products; Unified Access Gateway(UAG) and the Threat Management Gateway(TMG). In short the UAG is now used for inbound security and the TMG is used for outbound security. More details can be found here.