How can I see what kind of sections are on my page?

How can I see what kind of sections are used throughout my website? Each section doesn't have a name of what it is. It's like once you pick a section you don't remember what kind you picked before. I know I have a video section but I can't add videos from my computer. If it's a different kind of section however I can add a actual video from my computer that doesn't have to be YouTube or anything. Is there a way to change the section type without deleting the content?

If I want to not have the video section but a different section that allows multiple kinds of images and videos together, how can I change it from video to something else?

Like if I have a gallery section the captions aren't customizable. I want to change the section to a different type of section without losing the photos but allows descriptions/"captions" to be customizable. 

Thanks everyone. New here and I'm glad this exists for others to help.

Hi. Have you solved it yet?