Medium -- Paper used in forming the fluted portions of corrugated board.

Linerboard -- Paper used for the flat outer facings of combined corrugated board.

Burst Strength -- The force required to rupture corrugated fiberboard... measures puncture resistance.

Edge Crush Test (ECT) value -- The amount of force needed to cause compressive failure of an on-edge specimen of corrugated board... measures stacking strength.

Flute -- The wave shapes pressed into corrugated medium.  A, B, C, E and F are common flute types, along with a variety of much larger flutes and smaller flutes.
Illustration courtesy of the Fibre Box Handbook.