This section of the Help gives details on what each piece of Fission does.
-Main Window - An overview of Fission's main window.
-Secondary Control Windows - These secondary control windows of Fission contain additional controls.
-Save Panel - Fission's Save Panel enables lossless saving, as well as saving in other formats through QuickTime.
-Other Windows - Information on the other minor windows in Fission is found here.
-Menu Reference - This section explains what each and every menu item does in obsessive, boring detail.