A:Answer The main story is to battle 8 different areas (aka: gyms) and the leader of each gym to obtain a badge. Earning 8 badges allows you access to the end game, the championship league. A similar format to the gyms, you battle through to fight the strongest character to become the the champion. Side plots of the story include the new feature added to pkmn sword/shield, revolves around the mechanic "dynamaxing."
That is the casual extent of the game, which is fun to experience, however, the real value in pokemon lies in a few different areas that are not necessarily part of the story.
For some, its collecting them all to complete your pokedex, and for others its training your pokemon to battle against other ppl from round the world (or your friends). Those that are particularly pkmn enthusiast will learn to train their pkmn in a competitive standpoint, in which there are numerous websites to assist with the learning curve here.