Deleting "garrysmod" or Deleting Local Content?

When would you delete the folder garrysmod, and when would you delete local content (via Steam)?
Like what situation would call for which?

I just want to know if there is a difference and, if so, to what extent.

For my sake, I’m going to have to snip this.

-snip-

Don’t worry, it was nothing important.

Garrysmod folder should be deleted if you want a fresh install of the game. The local content should be deleted if your textures get corrupted.

For clarification:

Deleting the garrysmod folder just makes steam extract the files from the GCF again, Thus causing a fresh install of garrysmod

Deleting local content removes GCF and garrysmod folder, And makes you download the GCF from the steam servers again

Deleting local content doesn’t remove the gcf files.

Uhhh yes it does?

Then why is it, when I did so, it didn’t get me to reinstall anything?

If you want to have a basic download of GMOD, you do local and if you wanna get rid of it you delete that then go on steam and uninstall, then you can redownload it if you want and it will be gone.

This is the correct answer.

And what are in these GCFs? All the game data?

After understanding the above post:
OK, nothing is wrong with my installation (just want to clean it out), so I will delete the folder.
Thanks.