If a person, place, or thing is energetic and active, then it's dynamic. When things are dynamic, there's a lot going on.
Even the most exciting rural town won't be as dynamic as a big city: there are just more things happening in a city. Someone with a dynamic personality is probably funny, loud, and excitable; a quiet, mousy person isn't dynamic. You can also talk about the dynamic aspect of music, which has to do with how the music uses dynamics, which means "changes in volume." When things are dynamic, changes and energy are in the air.