One or more Recovered Files folder may appear in your Trash after restarting your computer. The recovered files are temporary files used by Mac OS X applications. Usually temporary files are deleted by an application when it no longer needs them. If an application quits unexpectedly, the temporary files may not get deleted by the application. When you restart your computer, Mac OS X moves these temporary files to the Trash.
You can retrieve useful files by dragging them out of the Trash. In most cases, however, the temporary files are not important and it is safe to empty your Trash. Check with the manufacturer of the application if you are not sure.