Just as with earlier versions of Windows, you will have a lot of temporary files saved in a variety of folders on Windows 10. In fact Windows 10 stores even more files that you may never need because it keeps the prior version of Windows every time you upgrade so as to allow you to roll back if you have problems with the new version. This backup of the prior version is in most cases kept until the next upgrade to Windows 10 is ready to be applied at which time it will be replaced by the files needed to roll back to the current version from the new one.
You can make your system run more efficiently if you remove unnecessary files. As with earlier versions, Windows 10 provides an option to allow you to delete all these unneeded files. The difference is that Windows 10 doesn't hide the option in the "Properties".
To clean up temporary and other unneeded files you first need to open File Explorer and select the Drive Tools - Manage option. This will open a new menu that contains the Cleanup option. This will bring up the "Disk Cleanup" dialog which will scan to see what files it thinks can be removed without affecting the running of your system and will then present you with a series of checkboxes next to a list of different types of files that you might want to cleanup (along with how much space you can save if you cleanup that group. This option looks and functions the same as in earlier versions of Windows except that you are also presented with a Cleanup System Files button. This button repeats the scan that was done before displaying the File Cleanup list but it scans a different set of folders. This extra set of folders includes the one where the prior windows version is stored. These extra options get added to the existing list of folders.
You can then select what to cleanup simply by choosing the checkboxes next to the groups of files that you want to delete.