The real advantage is that they’re not constrained by the physical limits on gas expansion, so they can throw projectiles at velocities of multiple kilometers/second. Doing that with chemical propellants, while not completely impossible, is highly complicated and prone to catastrophic failures.

Not that this one actually does that judging by the low speed and high lob… Guessing it’s a brand name and the actual gun works by a different mechanism. Especially where the barrel design is wrong to be a rail gun.