Texas regions are those defined by the Texas Association of Regional Councils . From that site "The geographic boundaries of regional councils in Texas must coincide with the twenty-four state planning regions designated and biennially reviewed by the governor."
There are many other ways to regions in Texas, but they shift their definitions over time and there are often disagreements over the definition.
The ODP Texas Regions category is based on the State Regional Planning Regions.
The East Texas Region includes Anderson, Camp, Cherokee, Gregg, Harrison, Henderson, Marion, Panola, Rains, Rusk, Smith, Upshur, Van Zandt, and Wood counties.
The Longview-Marshall and the Tyler Metropolitan Statistical Areas are within the East Texas Region.
The ODP Texas Regions category is based on the State Regional Planning Regions.
The Lower Rio Grande Valley Region includes Cameron, Hidalgo, Starr, and Willacy counties.
The Brownsville-Harlingen-San Benito and the McAllen-Edinburg-Mission Metropolitan Statistical Areas are within the Lower Rio Grande Valley Region.
The ODP Texas Regions category is based on the State Regional Planning Regions.
The Panhandle Region includes Armstrong, Briscoe, Carson, Castro, Childress, Collingsworth, Dallam, Deaf Smith, Donley, Gray, Hall, Hansford, Hartley, Hemphill, Hutchinson, Lipscomb, Moore, Ochiltree, Oldham, Parmer, Potter, Randall, Roberts, Sherman, Swisher, and Wheeler counties.
The Amarillo Metropolitan Statistical Area is within the Panhandle Region.