Economic imperialism is a form of how one country uses its economics to take control of another country. Essentially, this means one country is using its money and power to influence the decisions and policies of another country. It could be as simple as one country using its wealth to buy land in another, or it could be more complicated such as one country forcing the other to agree to specific terms and regulations for the economic relationship between them.
To use an example, let's say Country A is economically stronger than Country B. Country A can start to use its money to purchase things in Country B, like land and businesses. As they purchase these things, they can then set rules and regulations on how these things are used in Country B. This might mean that Country A has control over how Country B's businesses are run or how certain types of technology are used. They may also force Country B to buy things like food or weapons produced in Country A, making them dependent on Country A's economy.
In this way, Country A manipulates Country B and effectively takes control through their economics and policies. This way, Country A can control important decisions and how things are done in their favor, instead of allowing Country B to make their own decisions.