Doubt on project 3 data set shared.

In the Project 3 case study 2 one of the ask is to Analyse the retention of users on a weekly basis after signing up for a product. In the data set given what is considered to be a product and in which table. There is just a one liner given about the data set shared and is becoming difficult to understand. What is meant by retention of users since there is no column that indicates deactivation time of user. Please explain.