A more thorough explanation:

Definition: Colonialism is when one country or nation takes control of another country or nation, either fully or partially, and dominates it politically and economically. The country that is being controlled is called a colony.

For example, when the British Empire expanded outward, it practiced imperialism. The countries that were under British control were known as colonies. When these colonies gained independence, they became politically and economically sovereign, and collectively became known as the United States. However, colonialism still exists in the United States, as there are many indigenous nations present in the same territory.

Colonialism should not be confused with imperialism, which involves the use of military and economic power to expand and dominate. Colonialism is the occupation of the land after the imperial expansion.

Examples of colonialism include the colonization of Africa by European powers in the late 19th and early 20th centuries, the colonization of the Americas by European powers in the 16th and 17th centuries, and the colonization of India by the British Empire in the 18th and 19th centuries.

These examples illustrate how one country or nation can take control of another and dominate it politically and economically, often resulting in the exploitation of resources and people.

See also: terra nullius, doctrine of discovery, settler colonialism