People are bucketed into the following 4 status designations: Lead, Member, X-Member and Non-Member.
You can see this tag right below their profile pic on their detail page. This is assigned automatically based on the set of rules below.

The Rules:
Lead
Has no 'active' plans but...
Has a plan designated as 'Trial' membership.
Has been added to the system via 'Add New Lead' on Control Panel.
Has been added to the system via Lead Capture Form or Wordpress plugin.
Member
Has a active plan that is designed as 'Membership' plan.
Ex-Member
Has no current 'active' plans, but...
Has at least one membership plan with status of 'cancelled' or 'completed'
Non-Member
Has never had a plan that was designated as 'Membership'.
Disqualified leads will go into this bucket.
Any person that is 'deleted'