Hi Steve,

This feature is for access restriction to the plugin activation. In case you have some users except administrator with ‘activate_plugins’ capability and wish to allow them access definite plugins only at the plugins list (“Plugins” menu) to activate/deactivate.
1) Activate this functionality by turning on the “Activate per plugin user access management for plugins activation:” checkbox at the “User Role Editor” Settings page: menu “Settings”=>”User Role Editor”. In case you use WordPress multi-site, use Settings menu at the Network Center.
2) Check if user has “activate_plugins” capability
2) Go to that user profile and input plugins to which you wish to allow access
That’s it.
Did you look this support video?