Blonde Girl With Huge Breasts Strips Her Yellow Underwear In The Bed With Ballons

Air pressure, technically, is a measurement of the amount of collisions against a surface at any time. In the case of balloon, it's supposed to measure how many particles at any in any given time space collide with the wall of the balloon and bounce off. However, since this is near impossible to measure, air pressure seems to be easier described as density. The similarity comes from the idea that when there are more molecules in the same space, more of them will be heading towards a collision course with the wall.
The first concept of air pressure within a balloon that is necessary to know is that air pressures "try" to even out. With all the bouncing against the balloon wall (both interior and exterior) there will be a certain amount of expansion/contraction. As air pressure itself is a description of the total forces against an object, each of these forces, on the outside of the balloon, causes the balloon to contract a tiny bit, while the inside forces cause the balloon to expand. With this knowledge, one would immediately assume the a balloon with high air pressure inside would expand based on the high amount of internal forces, and vice versa.
This would make the inside and outside air pressures equal.
However, balloons have a certain elasticity to them that some needs to be taken into account. When you stretch a balloon, you are filling it with potential energy. When you let it go, the potential energy is turned into kinetic energy and the balloon snaps back into its original position (though perhaps a little stretched out).