There are two kinds of files that Twine works with: story files, which are editable versions of your stories that you can only open with Twine, and output files, which are read-only versions that can be opened in a Web browser. While you write your story, you make changes to your story file, then check to see what the output file looks like. When you're done, you can post your output file to a Web site or e-mail it to others.
Twine story files have a .tws file extension; output files are saved with a .html extension. If you've worked with Adobe Flash before, the situation is similar to Flash's .fla and .swf formats.
When you start Twine, it presents you with a blank story file. You can use the Save Story and Save Story As items in the File menu to save your work to your computer, and Open Story to retrieve it later. Twine also keeps track of story files you've recently used in its Open Recent submenu.
To create an output file, choose Build Story from the Build menu. This asks you to choose where the output file is saved, and then opens the resulting file in your Web browser so you can see your work. Once you've built an output file once, you can rebuild it in the same place by choosing Rebuild Story. The View Last Build menu item opens the most recent build in your Web browser.
If you're in the process of writing your story and wish to quickly review changes, the Test Play option lets you build and play a temporary HTML file which doesn't need to be saved to a directory. You can also begin a test play from a particular passage by right-clicking it and selecting “Test Play from Here”.