Ask HN: Can someone explain the common open source licenses?

Could someone roughly explain the differences between the common open source licenses out there (Apache, GPL, MIT, etc.) and any restrictions they may have?

I'm not working on any specific project that would require professional legal advice. I just want a basic understanding of the differences between the most common licenses and how they can generally affect or restrict projects.

What is the most open and unrestricted license? What licenses have restrictions I should be aware of? etc. etc. Thanks