A lead magnet is a free piece of content that you give away to your visitors in order to capture their email address. This way you can build your email list faster than with just a newsletter subscription. Examples of lead magnets are free ebooks, free courses, free whitepapers, webinars, a free book chapter, free checklists and so forth. They are usually offered as a content upgrade for blogposts, so that the visitor can learn more about the subject and you will become an authority in their mind.