This plugin allows Bitlbee to communicate with Mastodon instances. Mastodon is a free, open-source, decentralized microblogging network. Bitlbee is an IRC server connecting to various other text messaging services. You run Bitlbee and connect to it using an IRC client, then configure Bitlbee to connect to other services, such as a Mastodon instance where you already have an account. The benefit is that you can now use any IRC client you want to connect to Mastodon.