What effect did Alexander the Greats conquests have on Greece?

With his conquests Alexander spread Greek knowledge, language and culture and mixed it with the culture of regions he conquered. While doing that he respected the diversity and differences that now existed in his Empire. That period is therefore known as Hellenism.

Explanation:

Unlike many other rulers, Alexander believed that his task is not only to conquer different regions, but actually to unify the whole world, by spreading and sharing knowledge and blending cultures. During his reign even a common language was used on the soil of his kingdom, so everyone had a chance to communicate.