With Xbox finally showing off gameplay for Halo Infinite, the sixth mainline entry in the popular first-person shooter franchise, we figured it would be the perfect time to go back and chart the series' evolution. From 2001's Halo: Combat Evolved to 2020's Halo Infinite, the franchise has seen quite a few changes over the years.In the video above, Persia details those changes over the course of Halo's six mainline entries, throwing in a few words for the franchise's notable spin-offs, Halo 3: ODST and Halo Reach. Some of the changes have been narrative driven--Halo 2, for example, introduced a new playable character in the Arbiter. However, some changes were more gameplay-focused, like Halo 3's introduction of split screen co-op in the main campaign.Halo hasn't merely changed on the campaign side either--it's multiplayer has seen numerous overhauls over the course of the franchise's history. Halo 3: ODST, for instance, introduced a brand-new horde mode called Firefight and dropped dual-wielding altogether. But there have been more transformative changes as well, the most notable of which has to be Forge mode. Not only did Forge mode open up the floor for the community to create its own maps, the addition led to the creation of game types that were so popular that developers Bungie and 343 Industries would go on to recognize them as permanent game modes, like Grifball.If you're looking to catch up on Halo's story prior to the Holiday 2020 release of Halo Infinite, then your best bet is picking up Halo: The Master Chief Collection. The collection contains Halo Combat Evolved Anniversary, Halo 2 Anniversary, Halo 3, Halo 3: ODST, Halo Reach, and Halo 4. Other than Halo 5: Guardians, that's every game that Persia talks about in the video above.