Searching 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 minimap. You must stay still to search, as moving will cancel it (though any traps or breakable walls discovered before cancellation will remain discovered).
The default key for searching is Z.
Only rogues have full search range, which spans the entire minimap. Other races have only half of that range, which means that you'll need to search more often when your character is one of those races. The skeleton appears to have a slightly higher range than the monster races as well, though still not as much as the rogue.
You can get extra XP from traps and walls if you expertly disarm or discover them. This simply means finding and disarming them without discovering them by searching or triggering them first. 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, since the visible portion is limited to a few black pixels on the ceiling above the trap's location. Once found, however, they can be easily disarmed without triggering.
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 vertical shaft, empty except for fake walls that automatically retract, with a seemingly solid block at the top. If one can see identify the block or use the minimap to identify the shaft's location, expertly disarming it is possible. Secret tunnels can sometimes be accidentally disovered by walking into them, and counts as an expert discovery because it is not a trap and finding it this way would not count as "triggering" it. They can also be accidentally discovered by hitting them with a ranged or throwing weapon.