From the official website: The Celebrations expansion includes a subset called the Classic Collection, which features cards from the entire history of the Pokmon TCGall the way back to the Base Set
When it arrives to the battlefield you do...well let's see...a lot of things
Akoum Firebird Akoum Hellkite Akoum Stonewaker Belligerent Whiptail Emeria Shepherd Geyserfield Stalker Grove Rumbler Guardian of Tazeem Guul Draz Overseer Jaddi Offshoot Makindi Sliderunner Murasa Ranger Omnath, Locus of Rage Ondu Greathorn Oran-Rief Hydra Retreat to Coralhelm Retreat to Emeria Retreat to Hagra Retreat to Kazandu Retreat to Valakut Scythe Leopard Snapping Gnarlid Territorial Baloth Tunneling Geopede Undergrowth Champion Valakut Predator Wave-Wing Elemental
The biggest difference between Vintage and other formats is the huge card pool
Green: Green is the worst performing color both because its cards arent great, and also and more importantly because there are multiple green archetypes that are essentially traps
The game includes new tournament structures, special challenge matches, and secret opponents that unlock after meeting certain conditions