Every practice session is recorded as an MP3. When you get your Performance Report you can listen to your recording or choose to save it elsewhere.
Recordings are kept while you still have enough disk space reserved for them. How much disk space to use is configurable in the program Options. You can also choose to keep an individual recording forever, and it will not be automatically deleted, even when you run low on disk space. To keep a recording forever, open its Performance Report and check the Keep Performance Recording Forever in Library.