One of the reasons we can't build a practical fusion reactor is that we need to make very powerful electromagnets. Doing so requires a lot of electricity going through big circular circuits. Doing that without a superconductor creates too much heat and the whole thing melts.

They're trying to build them with existing superconductors instead, but those require super cold temperatures or super high pressure.

This is (maybe!) a superconductor that's cheap and exists at normal temperature and pressure.

It's got some deficiencies that would prevent it from being used in a fusion reactor, but it's existence may teach us how to build a better one that will work.