In detail
The local 3-pack (or map pack) is drawn from Google Business Profiles. Google ranks listings on relevance to the search, distance from the searcher and the prominence of the business, including reviews and links.
Appearing in it usually brings more calls and direction requests than a normal organic ranking.
How this relates to our work
Local 3-Pack comes up most often in our SEO / SEM work. Technical SEO, content and paid search that put your business in front of people already looking for it.