We rank candidates in the pool using a points-based system called the Comprehensive Ranking System (CRS). When we hold Express Entry rounds of invitations, we:

  1. choose the type of round we’ll hold
  2. decide the number of candidates we need to invite
  3. identify the highest-ranking candidates from the pool who are eligible for the chosen round type
  4. invite these candidates to apply for permanent residence

Read more here: https://www.canada.ca/en/immigration-refugees-citizenship/services/immigrate-canada/express-entry/submit-profile/rounds-invitations.html