WHat separates my townhouse from the next?

[badhaircut]

Hi there, I recently purchased a townhouse. The home is in Holland Landing, Ontario (just north of Newmarket) and was built in 1997. I don't know the name of the builder and I would like to know what exactly separates the townhouses.
I removed a receptacle and noticed that there is another sheet of drywall behind it. Is this drywall actually the back of my neighbors drywall or is this some sort of separation between the units?
Another reason Im asking is because I am planning to mount a television to this wall. The tv wall mount uses 3.5" lag bolts and the walls are built with 2x4 studs. I would hate to accidentally bulge my neighbors wall or possibly hit an outlet, pipe, screw belonging to their unit etc
Thanks for reading

[Markus Keller]

I don't know what Ontario requires so obviously there may be differences. Typically though, townhouse separation is either cement block walls or multiple layers of drywall. In this case it sounds like a framed wall with drywall. There are probably two layers of drywall on your side and two layers on the neighbors side of the framing. It could also be a double framed wall; which I have seen but doesn't get done often. Is the drywall that you see grey or white?
Figure out if the framing is wood or metal. If wood, you can use the lag bolts. If metal the lag bolts won't do anything. You'll need to use properly sized anchors or butterflies.