Answer:
A comma in a sentence is a pause, or a breath to extend a sentence.
Step-by-step explanation:
An example would be:
My friend John has a black and white spotted Dalmatian whose name is Ricky.
This is a sentence you can say all in one breath.
In contrast, a sentence you cannot say in one breath would be;
My next-door neighbor John has a big black and white spotted Dalmatian with a red collar named Ricky and a small schnauzer dog named Pizza.
To correct the sentence above you would say:
My next-door neighbor John has a big black and white spotted Dalmation, with a red collar. He also has a small schnauzer dog named Pizza.
I hope this helped!