Twitter has Twitter Lead Gen Cards, which let you generate leads directly within a tweet without having to leave the site. A user's name, email address, and Twitter username are automatically pulled into the card, and all they have to do is click "Submit" to become a lead. (Hint for HubSpot users: You can connect Twitter Lead Gen Cards to your HubSpot Forms. Learn how to do that here).
In marketing, lead generation is the initiation of consumer interest or enquiry into products or services of a business. Leads can be created for purposes such as list building, e-newsletter list acquisition or for sales leads. The methods for generating leads typically fall under the umbrella of advertising, but may also include non-paid sources such as organic search engine results or referrals from existing customers.