GOS is not a transaction but the button which appears one the top left side of the screen in a lot transactions. it includes usually 3 workflow entries: overview, archive and manual start. because it's very common you can use it as a generic way to display workflow logs for the transaction (to be more exact - the object the transaction is working on)
see. Object Services Toolbox - Generic Object Services (BC-SRV-GBT) - SAP Library