a Township is usully made up of 36 sections...Keep in mind sections are not always a square mile, and more than 36 sections may be present. This is especially true around rivers where there were French and Spanish land grants (arpents). The Township and range is simply a coordinate system like longitude and latitude.
It works as follows each Township/Range constitutes a 36 square mile area. This equates to 36 sections, each of which is one square mile/640 acres. I do note The_Baron's comments on this matter, but most of NW Louisiana conforms to the Township/Range/Section as far as I know.