You need people to host LAN parties (ofcourse, duh!). You also need the games installed on the systems of each and every participant. Then you need a LAN hub, which you can purchase from any PC hardware shop. Hubs are of different capicities, some can support 5, some can 8 and on and on. Then each participant needs to have an ethernet wire. Connect the systems by plugging the ethernet wires into the hub and configuring your IPs in the same range. Then one participant can host and others can join in.
There you go, you have a LAN party!