Capsules are mostly used in Dragonball.Goku was afraid of it when Bulma grapped some.
Goku thougth Bulma and those capsules were monsters.
Luckily he now knows better!I'm gonna give a small list of where these capsules where 
used from.Since i've only read 2 Comics yet i can only give some.
But i'm trying to collect them all so pleaz be patient:
1.A House.This was where Bulma and Goku slepped for a day.
2.Motorbike.Well,it was just to ride on and Goku used it 2!
3.Freezer.Trunks used this one to get some Soda of the 'Casuled Freezer'.
4.Soda.Actually,this soda was yet in the Freezer,so this wasn't really a capsule.
Well,that's about it for now.I hope you've seen what Capsules are or if ya
have understand it.It looks like a tampon[LoL] and throw it on the ground,and an item 
drops out...