There are probably books about the art of communication.

Using the example you gave, you were waiting with your daughter’s friend’s mom. She shared something about herself with you. She was probably just making conversation to fill the time and saying how she also cared for her nephew in addition to her daughter whom she was waiting for with you.

You might have responded with something validating that showed you heard her; like “It’s nice that you are able to help your sister” or something like that. Then she’d answer back with more on that subject and so on.

Conversation is sharing of information and ideas, connecting with others even just to pass time.