What are these blue handles?

[PerryPride]

Hi everyone! What are these blue handles? And the blue section on the layer?

When I remove them I cant extend or shorten the comp when I've imported it into Premiere. So I guess it has something to do with that, but what is it called and how do I add them my self?

[Mylenium]

You might want to read up on protected regions and responsive design time in templates in the online help.

Mylenium