Lets say I did a check out, edited some stuff and realized I want to re-download the repository code and overwrite my local changes without commiting them.
I downloaded
If you just update then Subversion will merge the changes made in the repository into your local copy. An update won't cause your changes to be sent to the repository.
To remove your changes from your working copy, select the files/directories you want to revert and choose Revert from the TortoiseSVN menu.