isochrone, “equal time”, map tells you where you can go within 10 minutes of walking (or biking, driving) from a starting point. It’s useful when finding a place to live, so you can be within 10 minutes of walking distance from a public transportation stop. Or if you’re looking for a place with multiple people, find the intersection that puts you within 15 minutes to your office, 25 minutes by car for your roommate, etc.
An idea I’ve had to improve isochrone maps is to make a multi-mode transportation option. If you work in an urban area, you may be taking walking and taking the subway to work. Or scooter and bus. Then you would see an image of a branching isochrone region – trunks where public transportation can move you quickly and bubbles around stations and stops.