On DigitalPoint Forums, a user summarizes the features:
Now with Google Maps you can create and share personalized, annotated maps of your world. Mark your favorite places on your map. Draw lines and shapes to highlight paths and areas. Add your own text, photos, and videos. Publish your map to the web. Share your map with friends and family.
Google made an official statement acknowledging the new functionality as well.
When you go to Google Maps, you can now see a new tab that introduces you to My Maps.
When you click on that tab, you are invited to "Create a New Map." Here's a map I created.
First, I titled the map:
Then, with the tools available to me (placemarks, lines, and shapes), I personalized my map.
I showed you where I landed, using a Placemark, and where I was headed, using the Line Tool.
I then used the Shape Tool with embedded HTML for an attached image to give you a picture of how close I was to a recent newsworthy event.
This was surprisingly a fun experience and was really easy to use. I could see it being used for historical purposes (teaching) and even for mapping out possible road trips. Truthfully, the possibilities are endless.