ISIS-K: Who are they?

NOTE: This video was recorded prior to Thursday's explosions at Kabul Airport.
The Taliban takeover of Afghanistan may have been swift, but things might not be as simple as they seem.
An offshoot of ISIS has cropped up in the region, and fears are growing that a terrorist attack is imminent.
It's certainly enough to worry the White House, and ISIS-K isn't exactly friends with the Taliban either