1. Yes, there is a significant difference between a works cited and a bibliography. A works cited will only list sources you've used in your essay, article, term paper, etc. If you've mentioned the source in your piece, it must be notated in the works Cited.
A bibliography lists all the sources you've used in the preparation of your piece. For example, if you went to Wikipedia as a resource, but did not directly use that material in your essay, it's appropriate to include Wikipedia in your bibliography. If you watched a video to collect ideas and take notes for your essay but did not use a quote or material from that source, you would still include the video in your bibliography.
Think of a bibliography as a complete collection of everything you've used to support the thesis of your essay, whether or not it made it into your final paper. This archives every bit of research you've put into crafting your essay while giving credit where credit's due.