Have you ever been watching a funny movie, cracked up laughing and suddenly... a little pee has come out?
This is a type of incontinence called 'stress incontinence'. It happens when you add extra pressure to your abdomen by moving suddenly, like you might when you cough or sneeze, lift or jump. The reason things get a little damp is that your pelvic floor muscles can't deal with that extra pressure very well; they get a little lazy and allow some pee to leak out.