In the commitment stage, a certain number of users must "commit" to using the site, which is simply a pledge to use it when the beta launches. Once enough people have done this, the beta version of the site will launch.
Here are some of the top physics example questions on the proposal:
Exactly what kind of data did Kepler work out his laws from?
What type of instrumentation was used to produce monofrequency light sources at the period of JC Maxwell?
When was it recognized by scientists that the surface temperature of Venus must be extremely high compared to the earth?