Select this option if you would like BCS (Business Connectivity Service) data to be imported. If you clear this selection, ...

Select this option if you would like BCS (Business Connectivity Service) data to be imported. If you clear this selection, your AD and/or LDAP connections will be included in the profile synchronization run (full or incremental) but your BDC connections, if any, will be ignored. You can change this setting later to include the BDC data import.