Rotate
Below you will see an image about to be Tilted, which is a 45° rotation.
Restore
There are a number of filters available. As with rotations or adjustments, all changes you make are commited to a temporary file only, unless saved to a file or the clipboard. All modification are "undone" all at once with the Image -> Restore original.
Adjust
Enhancements (adjust) tweak the listed parameters a little at a time. Use one several times to make larger changes.
Filter
Filters can create a bit more radical changes, which can be interesting and a lot of fun...
