From Eterna Wiki
Raw data is what we call the white and dark likes that comes from the process called electrophoresis. The dark lines are called bands. A dark band means that a reaction has happened. This means that the base is single. If the base had been paired to another base, it would have been protected, so it would not have reacted.
==Teaching about Raw data==
Pablo gave a fine explanation on how to read the raw data, under his presentation at the first monthly live developers meeting.