What is the difference between inbound and outbound marketing?

Inbound marketing focuses on earning, not buying, a person's attention, which is done through social media and engaging content, such as blogs and white papers. This content is interesting, informative and adds value, creating a positive connection in the eyes of the consumer, thus making him more likely to engage your brand and buy the product. So it costs less than the outbound marketing.I believe that outbound marketing techniques are getting less & less effective.