What it means to hear someone

We have at least an implicit and visceral sense of what it means to feel heard by someone. So what does it mean when we have a sense we are hearing someone?  What does it mean we know someone feels heard?

It varies. Sometimes we feel heard when others agree with us, when there is similarity of view. Sometimes we feel heard when it's clear to us that someone shares with us some longing. In these exchanges, we feel heard. To hear someone then means  listening for and validating similarities and longings.