Answer:
Independent executive agencies of the American government are those that, while in the technical aspect are part of the executive branch, govern themselves and are not ruled by the head of the executive power. One of the many responsibilities these kind of agencies have is working closely with the government to make rules.
On the other hand, government corporations are agencies that are in charge of business management and manufacture products for the country, selected by the President and the Senate. In most cases, these are monopolies and are more or less independent from the president.