Question

what is a couple?examples with explanation

Answer 1

It is used to express something in number two or approx.
e.g. Give me a couple of seconds.
It is also used to convey two people partners to each other (husband and wife.)
e.g. The couple stayed at cafe for some time.

Answer 2

A special case of moments is a couple. A couple consists of two parallel forces that are equal in magnitude, opposite in sense and do not share a line of action. It does not produce any translation, only rotation. The resultant force of a couple is zero. BUT, the resultant of a couple is not zero; it is a pure moment.

For example, the forces that two hands apply to turn a steering wheel are often (or should be) a couple. Each hand grips the wheel at points on opposite sides of the shaft. When they apply a force that is equal in magnitude yet opposite in direction the wheel rotates. If both hands applied a force in the same direction, the sum of the moments created by each force would equal zero and the wheel would not rotate. Instead of rotating around the shaft, the shaft would be loaded with a force tending to cause a translation with a magnitude of twice F. If the forces applied by the two hands were unequal, there would again be an unbalanced force creating a translation of the "system." A pure couple always consists of two forces equal in magnitude.

The moment of a couple is the product of the magnitude of one of the forces and the perpendicular distance between their lines of action. M = F x d. 
I hope my answer help to u and right