IIS Logs are generated from the Web Server that is IIS. These logs primarily contain information such as Who accessed the application, from which IP, what is the HTTP Status codes etc. It almost never indicate what is going on in SharePoint.
Coming to ULS, these are generated by SharePoint Application. These are far more detailed and will shed more light into inner working /errors generated by SharePoint. This includes logs from Service applications such as Excel Web services, Search, User profile synchronization etc.
https://social.technet.microsoft.com/Forums/msonline/en-US/2d93e5cd-cef5-4461-b844-c4a8eff84fbf/difference-between-iis-logs-sharepoint-uls-logs?forum=sharepointgeneralprevious
Comments