Anything used to obscure the front-facing camera on a computer. Often a piece of tape,; a jerk curtain could be anything temporarily or permanently affixed to a computer and or front-facing camera that obscures visibility.
Did you see how many jerk curtains were up in that picture of the Apple offices?
In wrestling, this is the term for the match that goes in-between two big storyline enders, to calm the crowd down. Also referred to as a buzzkill match.
Randy Orton vs. Mick Foley Hurricane & Rosey vs. La Resistance <--
HBK vs. Triple H vs. Chris Benoit