wat is point and plane of application(structures and stability?

Answer 1

i think plane is the path and piont is where it hits

Answer 2

I don't know what they mean in engineering terms, but they could imply application of pressure/force/torque. The way pressure (force on area), force (the reason of movement or deformation of a body) or torque(the reason of angular movement = spinning, going round) is allocated on a structure is important for the stability of it(that it doesn't fall, it resists gravity, air etc).