This is the Auran Trainz Content Manager, which is a necessity if you want to develop anything for Trainz. Why? Because all content for Trainz is compressed into an unreadable file that has to be decrypted every time something is edited, and re-encrypted whenever a mod is reinstalled or added for the first time. Yeah, it's really that cumbersome. The Content Manager isn't all bad, though, as it includes a number of handy content editors and built-in debugging tools.