John is a poor man who has a lot of problems. Some of his problems have to do with riding a bike. Some of his problems have to do with money, some with his children, some with his boring job, and some problems he has because he would rather live in the countryside than the crowded, smoggy city, which also happens to set off his asthma. Luckily, John's wife is the apple of his eye and the light of his life. So he has no problems with her. Her only problem with him is that he loves her so much.
Of all those problems, which ones do you want to know about?
Those he must face while riding a bike? Then that is a specific set of problems represented by the word the. For a small word, it is very important.
If you don't want to hear about all of his many problems, ask only about those problems he has while riding a bike (not the red bike, but any bike.)
I am interested in knowing about the problems John has while riding a bike.
All of the bold-type words are determiners. A determiner is a modifying word that determines the kind of reference a noun or noun group has: a? the? some? all? none? one? these? those? his? her? their? no? Here is a list of determiners.