Person synchronization is bidirectional. In the up direction, the Windows SharePoint Services site collection membership list is pulled into the Office SharePoint Server 2007 user profile database to inform Office SharePoint Server 2007 about which users are a member of which sites and allow incremental synchronization. In the down direction, the Office SharePoint Server 2007 user profile database sends down replicable user profile information for all members in the site collection.
For more information about incremental or full user profile synchronization, see Person Synchronization with Windows SharePoint Services.
You must associate job definitions with a service or Web application. You can also associate a job definition with a specific server. For more information about job definitions, see the Microsoft.SharePoint.Administration.SPJobDefinition class in Welcome to the Windows SharePoint Services 3.0 SDK.