Superconductors in general have no electrical resistance. That's basically electricity's friction.

Superconducting materials make the strongest electromagnets, they have big applications in quantum stuff (which I don't properly understand to try explaining), and they're used in something called a Tokamak, a specific kind of fusion reactor. They're useful in anything where electrical resistance is bad in general. When electricity is resisted, we lose some and get heat, so a superconducting wire would lose none and never heat up as a result of resistance.

Superconductors traditionally have to be super freaking cold. A lot of these applications can only be done with liquid nitrogen or even colder things, keeping them superconducting. You can do some things with pressure to help out with that, but the point is it's not easy to keep a material superconducting. This effort translates to costs, often prohibitive ones, as you need to actively keep these materials from collecting any heat.

If this research pans out, though, this kind of superconductor will just work at standard temperature and pressure. These could go into standard circuits, they can sit around without bleeding money on upkeep, they're very cool.

People are comparing them to transistors in part because before transistors we had vacuum tubes. Vacuum tubes do the same thing as a transistor, but they're effectively a lightbulb. They burn out, they produce heat, and they didn't miniaturize. Transistors were magic at the time because we could do so much more with them than vacuum tubes, and for superconducting metals, this is the same.