What is a socket? Just another bit of computer jargon? Devling a little into networking history, it is a Berkeley UNIX mechanism of creating a virtual duplex connection between processes. This was later ported on to every known OS enabling communication between systems across geographical location running on different OS software. If not for the socket, most of the network communication between systems would never ever have happened.
Taking a closer look; a typical computer system on a network receives and sends information as desired by the various applications running on it. This information is routed to the system, since a unique IP address is designated to it. On the system, this information is given to the relevant applications which listen on different ports. For example a net browser listens on port 80 for information. Also we can write applications which listen and send information on a specific port number.
For now, let's sum up that a socket is an IP address and a port, enabling connection.