Kinematics is the study of motion, without considering the forces which produce that motion. Kinematics of machines deals with the study of the relative motion of machine parts. It involves the study of position, displacement, velocity and acceleration of machine parts.
Dynamics of machines involves the study of forces acting on the machine parts and the motions resulting from these forces.
Plane motion: A body has plane motion, if all its points move in planes which are parallel to some reference plane. A body with plane motion will have only three degrees of freedom. I.e., linear along two axes parallel to the reference plane and rotational/angular about the axis perpendicular to the reference plane. (eg. linear along X and Z and rotational about Y.)The reference plane is called plane of motion. Plane motion can be of three types. 1) Translation 2) rotation and 3) combination of translation and rotation.
Translation: A body has translation if it moves so that all straight lines in the body move to parallel positions. Rectilinear translation is a motion wherein all points of the body move in straight lie paths.
Rotation: In rotation, all points in a body remain at fixed distances from a line which is perpendicular to the plane of rotation.
Translation and rotation: It is the combination of both translation and rotation which is exhibited by many machine parts.
Binary link: Link which is connected to other links at two points.
Ternary link: Link which is connected to other links at three points.
Quaternary link: Link which is connected to other links at four points.
Pairing elements: the geometrical forms by which two members of a mechanism are joined together, so that the relative motion between these two is consistent are known as pairing elements and the pair so formed is called kinematic pair. Each individual link of a mechanism forms a pairing element.
Degrees of freedom (DOF): It is the number of independent coordinates required to describe the position of a body in space.