The Three State Workflow, is by default disabled in Document Library but is enabled in Tasks in the Sharepoint Site.
Here we will see how do we enable the Workflow States which are greyed out by default.
When we open the Document Library and then go to the "Document Library Settings". Then we click on the link "Workflow Settings". We go to a page where we provide the Workflow name and then click on next button. In the other page, we get the section Workflow States and that section is greyed out. So we are stuck here when we try to create the workflow for the document library.
Here we have to create a column with the type of information in that column should be "Choice". And then add three options like, open, resolved and closed. Thats the reason why we call the workflow as 3 state workflow.
Once that column is specified, Now go ahead and create the workflow. Here in the "Workflow States" section you can see the options and the column name coming up without any issues.
If you try the same on the Tasks, you wont be facing such issue,as already that kind of choice column would be already present.
Hope this helps some onw.