The Windows registry is a database every Windows computer uses as a data and configuration storage. It is a good place to search for indicators of malware, since it includes dozens of places where software that wants to autostart needs to register.
The registry editor provided by Microsoft is very simple and missing a range of features that power users need, like a background search, easy to use bookmarks, tabs and more.
Safer-Networking wrote RegAlyzer to improve their own forensic work.