Before peeing: When a man really has to go pee and a drop of piss forms at the tip of
the penis. He really has to go.
After peeing: When a man pisses and finishes up quickly, by the time he zips up,
the last few drops of urine might not have left the urethra, so he might get his boxers a few drops of pee or so.
Could also
deal with semen instead of pee. Pre-cum before or remaining cum afterwards can cause leaky dick.