IRC is a form of instant communication over the Internet. It is intended for group (many-to-many) communication in discussion forums called channels, but also allows one-to-one communication.
irc://irc.freenode.net/puppylinux in your browser and then pick your nickname. If that doesn't work then with other IRC-capable programs like attym, Pidgin/Gaim, X-Chat, irrsi, etc. enter irc.freenode.net as the chat server and #puppylinux as the channel in the appropriate places.
Freenode Web Access site and any browser. You may either enter any nickname you wish but to use a Freenode registered nickname then check the box for “Auth to services” and also enter your username and password.
Freenode-hosted channel is subject to Freenode's policies.
For lots more, see our older IRC chat wiki page.