Of course we understand :) These are neutral buildings. We put them into maps, because we want to block pathes. You have to destroy it and then move on. Just like the mineral block system. There you place minerals, here we place "neutral buildings".
lol because they were placed in the map as neutral buildings to tighten or block an area. For example in my map (2)Inertia I placed a neutral building at the nat choke, thus tightening it. I did this instead of placing cliff there because 1. it forms a perfect edge against which a wall can easily be formed and 2. I wanted it to be able to be destroyed later for more room.
For Dreamcatcher, one use of the neutral is to block a path. This makes it so as if the path didn't exist early on, making defense easier, but can be destroyed offensively to make defense harder for your opponent or to form a way to scout by, or to open up yourself if you need an alternative route etc.