Aircraft use a number of technical terms.

Primary structure

The structure that takes the loads. Examples are wing spar, and tail boom

Secondary structure

The structure that makes the aircraft the right  shape. Examples are ribs and covering for the wings.

Centre of gravity

The centre of gravity, is the point in the aircraft (with pilot) where the weight of the aircraft can be thought of as acting through. It is the point where the aircraft balances, if you tried.

It is an important point as this is the point that the aircraft rotates around when controls are used.

This is the same point as the centre of mass.

Centre of pressure

The centre of pressure is a point on an aircraft where the lift can be thought of as acting through. for a straight winged aeroplane, the centre of pressure is in the middle of the wing, just over a quarter  chord back from the leading edge.

Glossary