I just downloaded Blender 2.79 after about 8 months of not using the software. I noticed that the "selection visible" function isn't working. I expect it to make the mesh partially transparent, but as of now, it does nothing. I am not sure what is going on. Thanks in advance for the help:)
Oh that was a tricky one...
it's just because you have collapsed the actual horizontal bottom bar of your 3D window, and the one we see is actually from another 3D window that you also have collapsed
so grip the bottom of your 3D windows and pull it up, them display its real bottom menu bar with the small "+" on the bottom right
and now you can activate the Limit Selection to Visible button