If a skyscraper is blocking the view of farmland you once had from your house window, urbanization is happening. Urbanization is a word for becoming more like a city.
When populations of people grow, the population of a place may spill over from city to nearby areas. This is called urbanization. Maybe tall apartment buildings spring up on what had been the outskirts of town, bringing more people there to live and work. Urbanization can also apply to how people live. For example, if they stop driving their cars and instead rely on public transportation, as most people in cities do, that's urbanization.