An electrical contractor in Austin, TX, posted a super-informative blog post about understanding AC and DC electrical currents. This is what the differences boil down to: "DC" means "direct current".

AC or DC: Which Is Better? Your gadgets run on direct current, but the electricity in your home is alternating current. What’s up with that?

AC and DC power differ in direction, usage, and efficiency. Learn the basics of how alternating and direct current work and where each is used.