Explain fuel cells
 

I dont understand what they are, can some one explain, thanks!

Please?

its like having a gas tank in your trunk...used in race cars, also with cars that run race fuel in their street cars...they have a small fuel cell that just holds race fuel

so its just a gas tank in the trunk

Commonly, they have a foam/sponge core within. This limits the amount of fuel that can be immediately dumped in the event that the fuel-cell is ruptured during an impact. Such a core also limits the sloshing of fuel during transitions.