When you reconnoiter an area, you’re looking around to try to get some kind of feel for the place. It often describes a military action, but you could also reconnoiter the breakroom on the lookout for doughnuts.
When you reconnoiter something, you typically explore it with a particular goal in mind. If you’re part of a military group, you might reconnoiter the coast to see where the navy might land. It’s a way to make a preliminary inspection so you can figure out what to do next. If you’re moving to a new city, you might reconnoiter several neighborhoods — you’re sizing them up to see if you might like to live there.