Google Maps shows a clever promo for Map Maker in the classic interface: "Is something missing? Edit Google Maps." It's probably an experiment, but the message always shows up when using this URL.
"Google Map Maker is a Google Maps service that allows you add or edit features, such as roads, businesses, parks, schools and more. Using Google Map Maker tools, you can visually mark locations and add detailed information about these locations," informed a Google post back in 2008, when Map Maker was launched. At that time, Map Maker was only available for 17 countries, including Cyprus, Iceland, St. Vincent and the Grenadines, Bahamas and Vietnam. Google continued to add new countries and the service now supports over 200 countries. "More than 40,000 people around the world are making contributions and improving Google Maps through Google Map Maker each month," announced Google in April, when the UK was added to Map Maker.
You'll usually see an option to "Edit in Google Map Maker" at the bottom of the map, next to the copyright message.