A bouncer is a type of software which proxies a users connection through a central server, so that when the user disconnects, the bouncer keeps the users nick connected. This way, the users IRC account is always online, instead of just whenever they have the Server opened in their client.
This had the benefit of logging all messages sent while the user was absent, so when they reconnect, they can see past messages.
KolymaIRC offers a service knowns as KolymaBNC, which is a free bouncer service that can be used on irc.kolyma.org.
Bouncers offer an array of other helpful benefits as well, including removing annoying identification commands, message logging, and an extra point of security.
How to get a bouncer account