Imagine a rectangular block placed on the slanting edge of a right-angled triangle. If the block is assumed to slide down this edge without any side movement, every point in the rectangular block experiences the same displacement and more importantly, the distance between the points is also maintained.
In a pure translational motion, every point in the body experiences the same velocity be it at any instant of time. A car moving in a straight line, the path of a bullet out of a gun are examples of translational motion.
Rotational Motion: Imagine a circular block going down the edge of the right-angled triangle. The points on the cylindrical body experience something much different than the rectangular block. Each point experiences a different magnitude of velocity in a different direction.
Rotation is what you achieve when you constrain a body and fix it along with a straight line. This means that the body can only turn around the line, which is defined as rotational motion. A ceiling fan, a potter's wheel, a vehicle’s wheel are all examples of rotational motion.