Rich text cells are the most common cell type to be added to a page, and as a result, are the default option when adding new cells. Rich text cells allow for the greatest variety of content within a cell, having a wide variety of tools to arrange and create content for your pages. A rich text cell uses what's called a WYSIWYG (What You See Is What You Get) editor bar to provide you with the tools as you work within the cell, and the experience is similar to that of a word processor.
For details on adding content to a rich text cell, see the Edit Mode section for articles that discuss each of the tools available to you when working with a rich text cell.