A more thorough explanation:

Major federal action refers to an activity or project that is undertaken by a federal agency or requires approval from a federal agency. This activity or project may have a significant impact on the environment, such as building a dam or constructing a highway through wetlands.

For example, if a federal agency plans to construct an aqueduct or dam, it is considered a major federal action. Similarly, if a federal agency adopts certain regulations that may significantly affect the environment, it is also considered a major federal action.

Under the National Environmental Policy Act, federal agencies are required to prepare and file an environmental impact statement (EIS) if they plan to take a major federal action that may significantly affect the environment. The EIS includes information about the potential environmental impacts of the proposed action and any public comments. This helps ensure that federal agencies consider the environmental consequences of their actions before making decisions.

Overall, major federal actions are important to consider because they can have significant impacts on the environment and surrounding communities. By requiring federal agencies to prepare an EIS, the government can ensure that these impacts are carefully considered and minimized as much as possible.