Scanning is an action that you can do in Red Rogue to search for traps and breakable walls. The area of effect is represented by a white square expanding out from your location on the mini-map. You must stay still to scan, as moving will cancel it (though any traps or breakable walls discovered before cancellation will remain discovered).
The default key for scanning is Z.
Racial Differences in Scanning
Both the rogue and the skeleton have extended scanning range, which can span the entire height of your mini-map. Other races only have half of that range, which means that you'll need to scan more often when your character is one of those races.
Expertly Discovering Traps and Secrets
You can get extra XP from traps and walls if you expertly disarm or discover them--that is, if you find and disable them without scanning and without triggering them. Fungal traps are the easiest to see but difficult to expertly disarm, since the difference between your disarming range and the trap's trigger range is very small. Dart traps are more difficult to see--their visible portion is just a few black pixels poking out from the ceiling--but can be easily disarmed without triggering.
However, breakable walls, pit traps and monster traps are indistinguishible from ordinary walls and floors until you interact with them, which makes them very hard to find without scanning. In fact, it may be virtually impossible to expertly disarm a monster trap because of the lack of visual cues. Pit traps on the other hand, can be identified if one has already been in the space underneath them. Beneath each one there is a long shaft empty save for the fake walls that automatically retract, with a seemingly solid block at the top. If one can see the seemingly solid block or use the minimap to identify the shaft's location, expertly disarming it is possible.