Why do some lines cut the plane and others don't

I'm completely lost here, and I don't even know the correct terminalogy to search for what I'm looking for.  I've been trying.

I drew an object (a cover plate) in sketch mode, and I disected the plane everywhere I wanted to pull it in different sections.   But when I enter 3D mode, only some of the lines are sectioning the plane and others are not, and I cannot find the difference.

Some of the lines I click on them and they don't even show any properties.

I'm hoping for help.