PowerPoint builds a sequence of slides for presenting to a room, not a document for someone to read alone — that one distinction shapes almost every design choice in it.
Each slide starts from a layout — a pre-arranged set of placeholder boxes for a title, text, or an image — so content lines up consistently from slide to slide.
The strip of slide thumbnails down the left side is how you reorder, duplicate, or delete whole slides — drag a thumbnail to reorder it.
View tab → Outline View shows just the text of every slide as a simple nested list, hiding all the visual design. Drafting the words for a whole presentation here first, then switching back to design it, keeps the two jobs from getting tangled together.