Hi Lydia. In English if we speak about someone being in bed it means that they are generally lying down with the covers over their body and either about to go to sleep or sleeping. If you are on the bed that means that you are probably sitting or standing on top of the bed and the covers, duvet or blankets. As children my mother used to tell us to get off the bed if we were jumping on it. But in the mornings she would say it is time to get out of bed :) I hope this helps.