Every design has a goal, so “The key to this approach is first to choose the right individuals to design for” from the book “In About Face: The essentials of interaction design” by Cooper.
It is great to know about the persona, a persona can help a product make more functionality by collecting user need, using problems.
We know who is going to use it, and then we design it to make our product more useful and helpful. The example given in this book is very interesting, which is designing different cars for different people with different goals. I am a fan of the car, it is very interesting to drive different cars. For me, I think each car has it own specialty.