This is what we call magnet content: content that you give away for free in exchange for email addresses. (thewritelife.com)
In content marketing, this can be done by offering rich content like an ebook to visitors in exchange for their email address. (sellbrite.com)
A lot of advice websites will send you a guide in exchange for your email address so they can SPAM you with a bunch of annoying offers. (meeting-women-online.com)