If The Associated Press Stylebook was created specifically for journalists, the target audience of The Chicago Manual of Style is much broader — all writing and writers.
A lead (also known as a lede) is the first paragraph or several paragraphs of a story, be it a blog entry or a long article. Its mission is to catch readers' attention and draw them in.
A good place to learn about journalists' rights and responsibilities is the code of ethics of the Society of Professional Journalists, which is widely used in newsrooms and classrooms as a guide for ethical behavior.