Why do ICs often have multiples of the same configuration, with different part numbers?
The first column in that table is "orderable device", which indicates that different codes won't refer to functional differences, but rather finishing and packaging.

From this document:


  SN74LS00D Standard part number
  SN74LS00DE4 Pb-Free + NiPdAu part number
  SN74LS00DG4 Pb-Free + NiPdAu + ‘green’ mold compound part number


That's also what timrorr refers to. Other differences in ordering codes may refer not just to the device package, but also how parts are delivered.



Here an "R" is appended to the ordering code to indicate "Tape and Reel" packaging instead of "Tube".