Sorry, I don't know how to explain properly. It's about the vocals and instruments doing same timing.
Here is an example:
and another one:
The general term for instruments and voices playing the same melody (rhythm and pitch) is unison, but it covers more than your cases: also when two instruments play the same melody or a choir singing the same melody. I'm not sure if there is a more specific (well-known) term which excludes those cases.
If only the rhythm is identical but not the pitch, it might be described as homorhythm or homometer, but again that is more often used for multiple voices.