Both these versions include two new expansion packs. The Definitive edition includes some new graphical options and what not (4k rendering / support). Both requires Steam and probably won't run on 98/XP. The versions on-sale digitally are the 2013 HD edition or the 2019 Definitive release. There's also fan patches that include a NoCD, some bug fixes, and Widescreen support. If you want play to play it online nowadays either play over Hamachi with some Bros or use Voobly. Getting this with the expansion is recommended. More detail, more customization, pretty much awesome all around, as long as you're into the RTS genre. AOE III takes over from here, but it just doesn't have the charm of the first two. The sequel takes you through the next 500 (actually, 1000 - from the fall of Rome, which was the 5th century CE, to about the fall of Constantinople, or 1453 CE) years or so, from the decline of the Roman civilization to the invention of guns.
