Greater city movements are when lots of people move to one city from different parts of the world. This can happen for lots of different reasons. For example, some people may move to the city to find a new job or to find a place to live that is more affordable than where they used to live. Other people may move to the city to be close to family or friends, or because they love the culture and lifestyle of the city. Many people also choose to move for educational opportunities. Whatever the reason, when a lot of people come together to form a big city, it's called a greater city movement.