There's a move tutor at route 212 and you can exchange your shards for moves
You cannot buy but you can teach your pokemon new moves in exchange of shards.
shards can be used to trade with other people. in return, they may teach your Pokemon moves. there are 3 move tutors in Pokemon platinum that will teach your Pokemon moves in exchange for shards in a specific color.
there is a man in the resort area who trades shards for moves you will have to have a pokemon that learns rock climb though. hope this helped
You can trade them in for moves at a move tutor
They can be traded for Pokemon to learn certain non-TM moves
It doesnt unless you have a TM or in exchange for coloured shards
Yellow Shards and the other color shards are used for trading with NPCs for items or moves. For example in Pokemon Ruby, Sapphire and Emerald they are the main source of evolution stones.
You can trade them to the move tutors so that your Pokemon can learn different moves.
You can use 10 blue shards to teach one of your Pokemon certain moves from move tutors.
There is a small house very close to Pastoria City and to it's left. In that house, you can trade the shards (10 for each TM) for weather changing moves. 10 red shards will get you sunny day, 10 blue will get you rain dance, etc.