Westernization is what happens when Eastern countries adopt cultural practices from Europe or North America. A McDonalds in Sri Lanka is an example of westernization.
If someone from a non-Western country — one that's not in the Americas, Australasia, or most of Europe — takes on values, culture, or behavior that comes from Western society, that's westernization. This can happen in many different ways, including adopting English instead of a native language, wearing typically Western clothes, abandoning a religious belief in favor of Christianity, or even watching Hollywood movies. A major downside to westernization is that ancient traditions and practices can be lost.