Judging by the number of boosted posts I’ve seen, this seems to be one of the most common tactics in a social media strategy. However, this tactic is really only useful if you understand what it accomplishes.

Engagement ads are designed to solicit people to like, comment or share (retweet or repin). The goal is to get people to interact with your content in some way. On some platforms you can then re-market to people who have had those engagements with your content. These are also fairly inexpensive ads that you can reach a large number of people with.