I have read about Translatory Motion it says

Question

"It is that motion in hwich body, which is not a point mass body is moving such that all its constituent particles move simultaneously along parallel straight lines and shift through equal distance in a given interval of time..

My question is that---
Q1. what are those constituent particles which are moving with the body?

Q2. what does the last line mean "shift through equal distance in equal interval of time"?

Answer 1

1) They could be atoms, molecules, ions, anything that has mass.
2) At the same velocity.