The beamer class is not the first LaTeX class for creating presentations, and like many of its predecessors, it has special syntax for defining 'slides' (known in Beamer as 'frames'). Slides can be built up on-screen in stages as if by revealing text that was previously hidden or covered. This is handled with PDF output by creating successive pages that preserve the layout but add new elements, so that advancing to the next page in the PDF file appears to add something to the displayed page, when in fact it has redrawn the page.
Source code for beamer presentations, like any other LaTeX file, can be created using any text editor, but there is specific support for beamer syntax in AUCTEX and LyX.
Beamer supports syntax of other LaTeX presentation packages, including Prosper and Foils, by using compatibility packages.
Beamer provides the ability to make 'handouts', that is a version of the output suitable for printing, without the dynamic features, so that the printed version of a slide shows the final version that will appear during the presentation. For actually putting more than one frame on the paper, pgfpages package is to be used.
An "article" version is also available, rendered on standard sized paper (like A4 or letter), with frame titles used as paragraph titles, no special slide layout/colors, keeping the sectioning. This version is suitable for lecture notes or for having a single source file for an article and the slides for the talk about this article.
Beamer depends on PGF for some of its features.