The session file can be thought of as a workspace and is most useful for re-creating experimental conditions. It does not contain any images or sequences, however it does contain the path to images that were open when the session was saved. It also saves any measurement tools that are placed on the image. If you use a session file you would normally save it along with a recorded sequence in the same directory. The next time you want to examine the sequence you should open the session file. It will automatically open the images associated with it as well as the measurement tools that were in place at the time.