Microsoft Test Manager is a tool that allows teams to plan, organize, track, and manage testing across their software lifecycle. It integrates with Team Foundation Server and Visual Studio to support test planning, creation of test cases and suites, manual and automated testing, defect tracking, and reporting. Some key capabilities include requirements tracing, status tracking, capturing diagnostic information during testing, and linking tests to automated test methods, builds, and virtual machine environments. It aims to support the entire testing process but requires other Microsoft tools and an initial configuration effort.