Matrix owes its name to its ability to bridge existing platforms into a global open matrix of communication. Bridges are core to Matrix and designed to be as easy to write as possible, with Matrix providing the highest common denominator language to link the networks together.
The core Matrix team maintains bridges to Slack, IRC, XMPP and Gitter, and meanwhile the wider Matrix community provides bridges for Telegram, Discord, WhatsApp, Facebook, Hangouts, Signal and many more.
Matrix can also be bridged to telco/SMS via another 3rd party service: