Vim is powerful text-editor, designed to be very user-friendly, so long as you're a pro-user. Short but obtuse key-combos, unintuitive (to most) editing, and arcane configuration. With experience, though, it can be an excellent tool.
The main way you configure Vim is with a .vimrc file. The configuration, though, is a language of it's own. The combinations are endless, and the level of customization you can achieve is one of the strengths of the Vim editor. A Vimbit is a line or small set of lines that, when put into a vimrc file, perform a certain task: remapping the escape key to something more convenient, limiting line lenght to 80 characters, setting a key combination to toggle whitespace visiblity, etc.
Sample Vimbit (credit to Steve Losh ) to make the oft-typed colon slightly quicker:
The state of the art for finding vimbits seems to be to crawl well-known Vim-ers' public vimrcs on github, or watch for "vimrc" threads on /r/vim, or follow vim-related twitter accounts. There are plenty of vim resources out there, but most focus on Vim as a whole- the basic commands, the modes of use, plugins, colorschemes, and configuration. Vimbits is here to focus entirely on that last one- the content of your vimrc.