This is great question and I don’t know how to answer this in 140 chars.

Since the days of print media to now, the format hasn’t changed much — there’s organic content interspersed with ads. The big advancements we made are in targeting and lowering the barrier of entry. Currently targeting is mostly confined to “Who you are?”. In future, it will also include — “Where you are?” and “What are you doing now?”. Instead of seeing Ad within content, you will see Ad within context of the current moment.