Furries are people that like anthropomorphic animals. And they make art of these anthropomorphic animals. A furry might have a fur suit which is a suit of their fur sona. A fur sona is like an oc that is an anthropomorphic animal.
Furries are not therians and therians are not furries by default. Some therians may also be in the furry community, and some furries may be in the therian community. But this does not inherently make one the other. They are separate things.