Athens is a very large city with a lot of smaller cities surrounding it. The traffic is usually pretty heavy, so driving is not always the easiest option, and if you can drive: good luck finding a parking spot! However, luckily, there are a lot of different options available to residents and fellow travelers like myself to get around the city, so let's talk about some of these alternatives!
In my specific city, Agia Paraskevi, everything is pretty walkable, and the majority of people take this option when they want to go someplace. But there is also the option to take a bus, drive, take the train or even take a boat! It always just depends on how far away the location is and what the weather is like. But walking and taking the metro are definitely the most common ways people get around. My favorite transportation method that I saw when I went to the Greek Island of Hydra was the local habit of getting around by riding donkeys because they don't have any cars on this island!
I basically walk everywhere, and when I first got here my legs were EXHAUSTED! Even now, a ways into my time in Greece, my legs are still very tired by the end of the day, but it was definitely a rough transition when I first got here because I was used to driving everywhere.