Whats in the Windows Old Folder?

[Juandisimo]

I updated to Windows 10 about 2 weeks ago and I've been noticing that a file on my ssd is taking a lot of space. This file is called Windows.old. Now my question is what is in this folder? Is it the old Windows 7? What will happen if I were to delete it?

Here is a picture of said file https://imgur.com/bkCZjl4

Any assistance regarding this matter will be greatly appreciated.

 

[Lmah]

It is the folder that is used to store files for reverting back to Windows 7 or 8.1 if you do not like Windows 10. If you want to delete it you can run disk cleanup which is built into Windows to clean up for free space.