The Arizona Instructional League (known informally as "Instructs") has been in continuous existence for well over 60 years.
This year, Cubs AZ Instructs will begin on September 20th and conclude on October 13th.
Typically, clubs will only assign players with experience below the AA level to Instructs, although occasionally an older player will be assigned to work on one particular phase of his game or to rehab from an injury.
Clubs with Spring Training homes in Arizona are not required to operate a team in the AZIL, and MLB clubs that do operate an "instructs" team are not required to schedule games against teams from other organizations.