When does one use Scrounging?

[Gnome]

Originally Posted by Kromm

Observation is scouting for criminal, espionage, military, or police purposes; it's for spotting guards, security, and counter-observers, and concealed vehicles and strongpoints.

I would love to hear more detail on use of this skill. I'm never sure how much I should focus on the "without letting others know that you are watching" part of the skill description on 211.