What are BTL advertisements?

Below-the-line (BTL) ads refer to a marketing technique in which nonconventional, non-media route is taken to promote a product or service. Usually, it has a limited target group. It includes promoting through e-mail, SMSes, ringtones, direct mail, MMS, freebies, quizzes, interactive sessions, etc. It is different from above-the-line (ATL) ads which take the route of TV, radio, cinema, banners, or newspapers.