This demo is a fictious video-streaming service that demonstrates several aspects of IRMA. When you become IRMATube “member” you receive membership attributes. Subsequently, you can use these to watch (trailers of) movies on the IRMATube main page.
In particular, the IRMATube demo illustrates the following aspects of attribute-based authentication.
Upon becoming member of IRMATube you receive two attributes: one which simply proves that you are a member, and one which contains a personal membership number. When you wish to watch a movie, only your membership attribute is requested, not the membership number that identifies you: you only prove that you are a member, not who you are.
In a more elaborate and realistic scenario you may want to reveal your membership number too in case you want a movie to be added to your profile. That is not included in the current version of the IRMATube demo.
Some of the movies on IRMATube have an age limit. When you wish to watch those movies, you have to reveal not only your IRMATube membership attribute, but also your age limit attribute. (These attributes can be obtained here or here.)