Learn English – the sense of the word “kettle” here

Are the following people or places?

The FLC traces the development of a person’s life along a path from

young and single, to
married with no children,
married with young children,
married couples with older children,
older married couples with no children at home....

To that list is added

empty nesters still in employment,
retired empty nester couples, to
sole survivor working or not working.

Note that empty nester is a compound word describing a person (not a place, I hope you can see)...

...so "nester" is not a "technical" or widely used term used to describe a person in terms of the life cycle of a human being. A "nester" could refer to a person who exhibits certain properties, such as Urban Dictionary's definitions 2 and 4.

Sometimes each part of a compound word is not used on its own to the same extent that the complete compound word is used, as in staple remover. Everybody knows what this is and uses it but remover is not used as often by itself, in American English at least.

Hearing is recognizing the presence of sound. You may or may not pay attention. Listening is the recognition of the sound or trying to process the sound and making an attempt to understand it.

In simple terms, when you look at the license/number plate of a vehicle, you visually "hear" the number plate. You may know there are numbers on it, you may recognize the colors, but you do not actually try to process the numbers and letters. When you "listen" to a number you know the letters and numbers in there, you know the color, you may even process the number to mean something that you can connect or relate it to.

In the third example, Joe was paying attention to Bob, but he was simply unable to understand. Hence Listen.

So hear is when you involuntarily sense the sound, Listen is when you sense the sound and pay attention to it.

Hope this answered your question. Sorry if my analogy was misleading or did not make sense. :)