The PPI shows how many interactions happen on a profile, how engaged the followers are and how fast a profile is growing. The higher the value, the better. A lot of engagement and healthy growth show liveliness and a lot of engagement, which depend on each other.
This indicator shows how active an account really is and how strong its ties to the community are. This KPI is especially important to gauge the real „image“ of a profile. A high amount of followers or tweets per day aren’t always indicators for a high quality account.