Setting a mark (
C-SPC) is probably the most frequent command I use besides basic navigation. The mark not only acts as a saved jump-to point, but it also sets the region. A region is what other editors might call a selection. By default, emacs does not highlight the active region, so it requires a bit of imagination to visualize it. To change that behavior, add this to your
(setq transient-mark-mode t)
This turns the Transient Mark minor mode on. In Transient Mark mode, when the mark is active, the region is highlighted.
Note: Some commands change their behavior when transient mark mode is on and the mark is active. Personally, I like the changed behavior, but invoke
C-h d transient for more information.