Why would you want to hide a slide that you spent all this time creating?!
The hide slide feature is helpful in allowing users to create backup or alternate versions of slides and info that they may or may not want to use.
If in doubt, don't delete it! Move the slide to the end of the presentation and Hide it.
This strategy is helpful if you want a few variations of slide options to test out. Or if you have some extra detail on a slide that you may or may not use.
You can still access the hidden slide in the slide show mode by entering the slide number and pressing enter.