The Pokemon Sword and Shield were released not too long ago but players have already started collecting an impressive list of Pokemon in their Pokedex and are looking for some of the rarer Pokemons in the game like the Shiny version.
While the previous game also had Shiny Pokemon, the new game will have two versions of Shiny Pokemon. There is the regular shiny Pokemon which sparkles with stars when you see them and then there is one that sparkles with squares with the latter being less rare as people have been encountering more of those.
Some people speculated that the square Shiny could be rarer but will appear more common if you use certain methods to find it while the star Shiny can only be found randomly.
However, there is no real answer on why there are two versions now and if there is really any difference between the two versions.