A more thorough explanation:

Definition: Federal land refers to land owned by the United States government. It includes all immovable and indestructible three-dimensional areas consisting of a portion of the earth's surface, the space above and below the surface, and everything growing on or permanently affixed to it. Federal lands are classified as public lands or acquired federal lands, depending on how the land was obtained.

Examples:

• Public lands: These are lands or land interests held by the government, without regard to how the government acquired ownership. They are unappropriated land belonging to the federal or state government. Examples include national parks, forests, and wildlife refuges.
• Acquired federal lands: These are federal lands that were never in the public domain. They are lands acquired by the government from private hands or from another governmental entity. Examples include military bases and government buildings.

These examples illustrate how federal land can be owned and used by the government for various purposes, such as conservation, recreation, and national defense.