There could be a set of changed files, which you don't want to commit and want to undo the changes that you have already performed. Select those files/folders and right click on them to open the Git context menu, where you can click Undo Changes... to discard them. The files will be reset to the unmodified stage:

Sometimes, before performing any commit or undoing the changes, you may want to check what has been changed since your last commit. You can do so by individually selecting a file, right-clicking on that, and clicking the Compare with Unmodified... option from the context menu to compare the changes side-by-side, as shown in the following screenshot:

You will find the removed lines or contents marked with a reddish background, whereas the changed or added contents will be marked with a greenish background.