Astronomical conjunctions occur when celestial objects appear close to one another in the night sky -- this happens all the time and they're not particularly unusual. But a conjunction happening tonight is notable in that it involves two very bright planets -- Venus and Jupiter -- and they will be closer together than they have been since Terminator 2 was in theatres.
Over the last month, the two planets have been drawing closer and closer together in the sky, with tonight's separation between them measuring only a third of a degree. As the sun goes down -- you don't even have to wait until dark since the planets are so bright -- look to the west, where you'll see the brighter Venus alongside the dimmer Jupiter. They will be so close together you'll be able to hide both planets behind your pinky finger.