Is a tract different than a section?
It may or may not be. A tract is a specific piece of land that has a deed conveying it to the owner. It may be an odd shape; it may be a quarter section or it could be many sections. In states like Oklahoma, it would probably not be a whole section since the land run issued smaller areas to individuals. In Texas, it could be quite large if part of original Spanish land grants. Given that many generations have come and gone since the original patents (first deeds), most tracts are much smaller due to the fractionation of families.
Generally speaking, oil and gas companies treat a tract as a piece of land with “common ownership”, i.e. undivided ownership. So, if Section “A” is 640 acres owned by Person “1” who then conveys an undivided 50% interest in the surface and minerals to Person “2”, the entire section is still a single tract. However, if Person 1 then conveys a 100% surface and mineral interest to Person “3” in only the NE/4 of Section “A”, then the NE/4 is a separate tract because ownership is different than the rest of the section where Person “1” and Person “2” are still both 50/50 undivided owners.
From the viewpoint of a mineral owner, the tract is the gross acres in which you own all or a fractional interest. If you own 1/4 minerals in NW/4 of a section containing 640 acres, then the tract is 160 acres and you own 40 net mineral acres.