DCBackup what the sims3 use this for and can it cleaned out without destroying the games or is it required and should it be left alone?

When you install something through the launcher, the game stores copies of those files in that folder. You can delete those backup files, except for one. Do not delete a file called "ccmerged". If you delete that file, then the store premiun content you have won't work right anymore.

Edit: Also, when ever you share anything, the game will check this folder to pack along any custom content you may have used in your creation. If the folder is empty, it will fall back on a standard EA replacement, even if the cc you used is still installed in your game.

This is a good, detailed info page about Sims 3 folder contents: https://nraas.wikispaces.com/Sims+3+Folder+Contents+FAQ