What is a project in FinalCut Pro? Seems to make no sense

Coming from real Pro Video Editing Software like Adobe Premiere Pro and Vegas I find Finalcut to be extremely unintuitive. The developers seem to be very different from the ones that made Logic Pro, which is phantastic and is becoming better every update. Not so Finalcut. It seems to become worse and worse. This funny timeline behaves differently from any other software that has normal tracks for video and audio like normal producers would expect.

The most terrible thing is the file and project management that I am unable to understand after a full year of trying. It is incomprehensible. Why is there a library. Why not just a project, like everybody else does it.

And if you open a project. Work something in the timeline. Open another project. Suddenly the timeline is already filled with the exact stuff that is in the other project. Ok. You delete it to start a new project. But, shocker, everything is deleted from the first project, too!!!!

This is chaos! Insane chaos! What is the new meaning of a project in the alien world of Finalcut? Please help a confused user that has worked with hundreds of projects in Adobe and Vegas and never had anything like this.