A member of social media site Tumblr has explained (in a little bit more depth) Pokemon’s timeline. They split up the GBA games, the DS games and the 3DS games into three different sections, the Elementary Dimension, the Connectivity Dimension, and the Infinity Dimension.
The GBA games (Elementary dimension) are where, as we all know, Pokemon was primitive. The poster essentially presents that each game presents a “What if” scenario within multiple parts of the same world. That world, like ours, is finding out more and more about Pokemon as we go along.
The DS games (Connectivity Dimension) is where we know more about the world, but there are still many more secrets to be discovered. The games further explore how trainers and Pokemon interact as well as other trainers and tie in the past dimension through lore.
The 3DS games (Infinity Dimension) is where everything ties back together. All Pokemon are known, there’s less and less secrets to explore, and the bonds between trainers and Pokemon have become all that much more commonplace, leading to extraordinary discoveries in battling like Mega Evolution and stronger bonds between trainers.