Personas - know your users
Personas are a great way of getting to know your users and understanding them. A reminder when designing and a way to ensure that the whole team is on the same page.
Sometimes you forget the different target users, maybe you relate to one more than another and this is why personas are good to keep close while designing. I usually have them in my sketching tool as well as any other type of framework (like a styleguide) to keep everything close and as a way to keep my design consistent and on the right track.
How to create a persona?
You can’t make a persona up out of pure imagination. A persona is based on research on real users. What kind of research is up to you but just by asking different kind of users a couple of questions can give an idea of one persona. The more users you interview the more personas you may find and if so you’ll probably need to prioritize since you shouldn’t design to please everyone. You need to know which personas are the most important and focus on them.