To create a new slide, click "Create Slide" at the bottom of the slides tab or "New Slide" in the Home tab, give the slide a name, and then hit create. This creates a new slide with the default positions of the objects parts. To duplicate the current slide instead, you can hit the "Duplicate Slide" button or press CTRL+D.
When you move objects around the scene, apply affects, move the camera, or do anything else, it is saved by the slide, and returning to that slide will restore all the properties to what they were when the slide was last edited.
For more information about slides, see the Slides documentation.
Now that we understand the basics, we can start learning some more advanced features.