A mIRC or IRC client is the software you use to connect to the IRC servers. There are literaly hundreds of different mirc scripts but they almost all use the same base that was written by Robby Pointer several years ago. It is called mIRC and it is used for PC's. There are also clients for Macs, Amigas, and there is a client script called BitchX for Linux
To download the clients click on the following links. mIRC for PC's mirc and eggdrop scripts mIRC for Macs mIRC for Amiga BitchX for Linux