PowerPoint straddles the presentation software market like a colossus, but if you only occasionally dabble in building presentation decks, then the terminology can seem pretty confusing. Microsoft's Crabby Office Lady blog runs through the basics for people who think placeholders belong on the dining room table.
The explanations of how to achieve particular features are based around the Ribbon-toting PowerPoint 2007, but the basic details apply to any PowerPoint release (and, to a large extent, to other presentation packages like Show). If you're a newbie to PowerPoint, it's also worth checking out how to fix common PowerPoint problems.
Demystifying PowerPoint terms [Crabby Office Lady]