To answer all of your questions, read frequently asked questions.
All major search engines such as Google, Bing and Yahoo have primary search results, where web pages and other content such as videos or local listings are shown and ranked based on what the search engine considers most relevant to users. Payment isn’t involved, as it is with paid search ads.
Bootstrap is a powerful front-end framework for faster and easier web development. It is a collection of CSS and HTML conventions. Learn more.