The persona template is used to personify the needs of the target group(s) of your planned project. This helps the team to get a deeper understanding of the project target group(s). The persona is a holistic fictional yet representative archetype of a given stakeholder group.
The personas are not stereotypes but archetypes based on research of the group and experience. When you put a face to your data, you make your insights visible and memorable.
This is particularly useful in the early stages of the project cycle.