Taking a Look at Autosave and Resume
One extremely helpful new feature that Apple added to Lion is Autosave. In TextEdit, Preview, Pages, and other Apple apps, the application saves your files for you while you are working on them. Each time the app saves the file, it saves a version of the file as it exists at that moment.
When you are finished working on a file, you can just close it without bothering to save it because Lion does that for you, too. All saved versions of a file reside in the file, so at any time, you can browse through the versions. You can restore an older version of the file, access an older version and copy something out of it, or save a version as a new file.
Apple has made it possible for developers of third-party software to include the Autosave functionality in their programming code. At this writing, many third-party applications do not use Autosave, but you should see the Autosave feature in more and more third-party software as time goes on.
With the new Resume feature, it's not even necessary to close your apps any more before you shut down your computer. When you shut down your computer while a file is still open, Lion not only saves the file for you but it also opens the file for you the next time you start your computer.
Everything is just as you left it[md]the text cursor is where you left it, text or objects are selected if they were previous to shut down, and any inspectors you had open are still open. Basically, you can just start your computer and everything will be just as you left it. If, on the other hand, you don't want to take up where you left off, you have the option when shutting down not to reopen your apps.