This thread is about the way typing is implemented into game design. And what purpose each type fulfilled in the games. This is only going to discuss gen 1 as it's the building block of later mainline pokemon games, So In the gen 1 games there are 15 types these are Grass, Fire, Water, Normal, Bug, Poison, Rock, Ground, Electric, Psychic, Ice, Ghost, Dragon, Fighting, Flying
Beginning of the game types
>Bug
The bug type was meant to serve as an early game mon to help you through the beginning of the game and then fall off overtime. This is further shown when most bug moves in gen 1 are pretty weak. These pokemon are meant to be tutorial's on evolution and help out trainers who need their higher than average stats at that point in the game. Example's of these pokemon include Caterpie and Weedle.
>Normal
Normal served an entirely different function, Mainly a decent all around type with few weaknesses making it a strong option for beginning trainers looking for pokemon that have longevity outside of rattata, Most of the early game normal pokemon can usually hang around for the remainder of the game. Examples include both Spearow and Pidgey.
>Poison
The poison type is the early status type, In that it uses a combination of the poison status to whittle down your pokemon and generally be pretty frustrating to deal with. The type is somewhat rarer as both nidoran's are found in one route and weedle overlaps with bug. Nidoran's line becomes part ground later which have a role as an offensive type. But right now they're mainly status absorbers. Until mt. moon.