This is a very good question. Let me explain with an example.
Lets say you love automobiles (interest). You read a lot of magazines about automobiles, you want to know about new trends, technologies and how different models and cars are different from each other. This is your interest driving you.
On the other hand, you are also an outgoing person who loves interacting with people, public speaking and love to build relationships with people instead of working by yourself in an office.
Now you could choose to combine your interest in Automobiles and your extrovert personality to work in Market Research in the field of Automobiles.
Market Research is an area that requires you to talk to people, read about automobiles, write articles and speak to the media about your analysis.
As you can see, you can build a career based on the combination of interest and personality.
On the other hand, there is another student who is interested in Automobiles but is more of an introvert less of an extrovert. He/She loves Physics, especially problems related to thermodynamics or aerodynamics. Give this person a problem and she will try to find a solution to it through conceptual knowledge and some collaboration