This is an imaginary jar that holds all the pointless/useless/worthless stories that are told by all people. Once a pointless story is told you cup your hands in the shape of a circle, thus creating the top of a jar. Luckily the jar is imaginary so it is limitless and easy to be transported to and fro.
"This one time, at band camp."
"Dude, that was horrible, put it in the pointless story jar"