The short answer
The Google Map Pack is the block of three local results shown with a map above the ordinary links. Winning it means ranking in that top three, which captures most local calls and directions. Google ranks it on relevance, distance, and prominence, with your Business Profile carrying the most weight.
What the map pack is, and why three is the whole game
Relevance, distance, and prominence
"Local ranking comes down to three factors: relevance, distance, and prominence."Relevance is how well your business matches what the searcher wants, driven largely by your Business Profile categories and the content that describes your services. Distance is how far you are from the searcher or the area they name, which you cannot change, though you can strengthen the other two to compete from a little farther out. Prominence is how well known and well regarded your business is, built from reviews, citations, links, and your overall reputation across the web. Of the three, your Business Profile signals carry the most weight, which is good news, because they are largely within your control. You cannot move your address, but you can choose the right category, complete every field, earn steady reviews, and build consistent citations. Distance is the one lever you do not hold, so the whole strategy is to win relevance and prominence so decisively that they outweigh a competitor's closer pin. Relevance and prominence are where nearly 95 percent of our effort goes on a new profile, precisely because distance is fixed. We have watched a business two towns over outrank the shop around the corner, not by moving, but by having the right category, recent reviews, and listings that all agree, while the closer competitor had none of it. That is the lesson we bring to every profile we touch: you cannot beat geography head on, but you can make the other two factors matter more than it.
— Google Business Profile Help
The primary category is your biggest single lever
Reviews: recency now outweighs a stale pile
"A steady stream of recent, authentic reviews tells Google your business is active, trusted, and currently serving customers."That means volume alone is not the goal, velocity is. In the review systems we install, the whole design goal is to ask every satisfied customer at the right moment and make leaving a review take 30 seconds, then respond to every review that comes back, positive or negative, since engagement is itself a signal and it reassures the next reader. Never buy or fabricate reviews, because platforms detect it and the penalty is severe. The pattern we see again and again is a business coasting on two hundred reviews from three years ago, watching a competitor with forty recent ones climb past it. We watch the map pack reshuffle after a run of fresh reviews more reliably than after almost any other single change. Old reviews are not worthless, but they read as history. A fresh, steady stream reads as a business people are hiring right now. Reviews do double duty here: they lift your rank in the map pack and they lift the rate at which a searcher who sees you actually chooses to call. Consistent, recent, well-handled reviews are among the highest-return activities in local search, and most competitors let them stagnate. The system that asks, every time, is worth more than any single five-star review you might chase.
— Google Business Profile Help