when searching for email why do I get results "Matching Leads" AND "Matching Contacts"

when searching for email why do I get results "Matching Leads" AND "Matching Contacts"

when searching for email on main screen upper right corner in search field, why do I get results in "Matching Leads" AND "Matching Contacts" for the same email address when in fact there is only one record in either Leads or Contacts.

Do Leads also have separate Contacts associated with them or is the Leads database a flat file with no "contacts" related in separate table/database.?
George