Like th4 said, those are the various wireless networks your computer can detect. The little dots and 90-degree arcs indicate the received signal strength, and only one is very strong. Were you able to connect to one of the weak sources your data up and download times would be horrible, with some data lost or incomplete. Looking at what my computer "sees" there are 9 other wireless sources of significant strength in my neighborhood. plus a couple of weaker sources. This being Silicon Valley, I'd be shocked if any are not protected.