How can networking in computer be useful in comparison to stand along computer?

With stand-alone computing, it's just you and your computer. You can access documents on your own computer and install programs from CDs. With networking, multiple computers on the network can access the same printer, share files with each other wirelessly, and play multiplayer games with each other over the network. The internet itself is also a network, so without computer networking you wouldn't even be able to be viewing this answer right now.