Take a look at the attached animated gif. Say the green Track is some background vocal ouus & ahhhs that have been comped together over the course of 1 bar. Notice that they do not align with the beat and bar lines.
I duplicated the green Track to make the blue one and then I selected all the short Audio Events and made a single Audio Part out of them. When I first made the Part it did not fill the entire Bar. The Part started where the 1st Audio Event begins and stopped where the final Audio Event ends. So with Snap on I dragged the bottoms of the start & end of the Part so it exactly fills the Bar.
Now it is easy to copy the Part and move it while still keeping all the audio in the same Bar/Beat position. Where if I try and move the Audio Events it is difficult to keep them at the correct Bar/Beat position.
This is what Audio Parts are for - taking a bunch of smaller Audio Events and grouping them together so they behave like a single Audio Event.