Newton's Third Law, also known as the Law of Action and Reaction, states that two bodies exert equal and opposite forces on each other:
$$\vec{F}_{1}=-\vec{F}_{2}$$
If one body exerts a force on another, the second exerts an equal and opposite force back.
It is the pair of forces that act on different bodies during an interaction.
Yes. It appears in walking, jumping, recoiling, collisions, and many other interactions.