How is pressure caused? and how it varies depending on the environment, use an example of a balloon

This can occur probably because of atmospheric pressure.  The volume of air inside the balloon (will be considered high inside the balloon; pressure occurs when a high concentration of particles are exerting kinetic energy to the walls of a container.  In this case, the inside of the balloon) however, if the pressure outside it is really high, the balloon will pop because there are many pressures on the exterior surface.  If it is medium like our atmosphere, it will be fine and probably float around. If it is too low, then it might pop or just change shape. 

^u^ I hope this helps you! and Good luck