Guides explain general topics and use cases (e.g. setup). API docs are automatically generated from the codebase and give specific details about functions, properties, and events.
There are a number of options that can be used to change how the player behaves, starting with the HTML5 media options like autoplay and preload, and expanding to Video.js specific options.
You can change the look of the player across playback technologies just by editing a CSS file. The skins documentation gives you a intro to how the HTML and CSS of the default skin is put together. For a list of skins you can check the [video.js wiki][skins-list].
You can package up interesting Video.js customizations and reuse them elsewhere. Find out how to build your own plugin or [use one created by someone else][plugins-list].
A "tech" is the shorthand we're using to describe any video playback technology - be it HTML5 video, Flash, . Basically anything that has a unique API to audio or video. Additional playback technologies can be added relatively easily.
A "hook" is functionality that wants to do when videojs creates a player. Right now only `beforesetup` and `setup` are supported. See the guide for more information on that.