Colonialism is when one group or country subjugates another group, often imposing laws, religion, culture, and languages on that group, and taking resources from them. Colonialism is often justified by belief that the subjugated people are inferior (e.g., barbaric, savage, godless, backwards), and the superiority of the group doing the subjugation (e.g., civilized, advanced).
Although Colonialism sounds like very immoral, because it is invasive and not built on equality, however, colonialism did fast and efficiently changed some country in history and made them more wealthy and developed. Like the former Prime Minister of Singapore, Lee Kuan Yew, says that "I am glad that the British colonized Singapore. We are grateful for their departure!" Lee Kuan Yew once said: "Most Singaporeans are descendants of Fujianese and Cantonese. Their ancestors were illiterate and poor. The key to Singapore's success is The rule of law system left by the British, not some Confucian culture."