Points are a way to quickly determine the reputation and popularity of ideas and users. The higher the point values, the more likely that idea or user is well established.
See the Point Award Grid
Users get points, for creating ideas, adding detail, having user interact with their ideas, and interacting with ideas of others.
Ideas get points for being created, having detail added, and having users interact (view, like, follow, express interest, ...) with them.
Engage Users - Increase Participation - Provide Instant Feedback
It rewards users for being active participants and thus encourages more active participation and also gives users a basis to judge the credibility of other users.
Go participate, it will all make sense soon.