What is a map listing?
For a shop with a door, this is usually the most valuable thing you own online, and it is free.
The listing and the profile are different things
The listing is what a customer sees. The profile is the free account where you decide what it says. People mix the two up constantly, and it matters because one of them you can edit and the other you cannot.
If you have never claimed the profile, the listing may still exist. Google builds them from other sources, which means there can be a version of your business on the map that nobody at your business has ever checked.
Why it outperforms the site
It sits above the ordinary results, it answers the two questions a walk-in customer has, and it carries the reviews. Somebody deciding where to go in the next twenty minutes rarely opens a website at all.
How to check yours in two minutes
Search your business name and your town on a phone. Look at the hours, the phone number and the photographs, and ask when each was last correct. Then read the profile guide, or why we usually start here.
Questions worth asking
Does it cost anything?
No. Claiming and running the profile is free, and the verification is usually a code sent by post or phone. Anybody charging you a monthly fee purely to keep it live is charging for something Google gives away.
Do reviews really change how often it shows?
They change how often it is shown and how often it is chosen, and the second effect is the larger one. A listing with recent reviews gets picked over an equally close one without them.
Updated