The Central United States is sometimes conceived as between the Eastern United States and Western United States as part of a three-region model, roughly coincident with the Midwestern United States plus the western and central portions of the Southern United States; the term is also sometimes used more or less as a synonym for the Midwest, leaving out all or most of the South.
The Census Bureau does not provide a standard definition of "Central" region of the United States, and organizations that need to subdivide the US are free to define a "Central" region to fit their needs.