What do the shards and stones do?

The stones evolve the pokemon. So you have to give a fire stone to Vulpix or a water stone to squirtle or something. And you give the shards to someone and they change them into a stone I think. Red shard = fire stone.

Well you exchange the shards for stones at the diving masters ouse then you use the stones to evolve Pokemon here are the Pokemon that evolve by stones.

Vulpix + fire stone = ninetails
Pikachu + thunder stone = raichu
Staryu + water stone = starmie
Lombre + water stone = ludicolo
Nuzleaf + leaf stone = shiftry
Gloom + leaf stone = vileplume
Gloom + sun stone = bellossom
Skitty + moon stone = delcatty
Jigglypuff + moon stone = wigglytuff

If you get shards, you can bring them to the shard collector near mossdeep city. He will give you stones depending on the color of the shard e.g. Red shard=fire stone.green shard=leafstone. Blue shard = water stone. Stones are used to evolve certaine pokemon. E.g. Leaf stone used on gloom= vileplum

You need the HM Dive them near mossdeep is a house were the Hunter lives go inside and talk to him he will tell you you can dive underwater to collect shards thats when you can go to dark spots in the water teach the HM Dive to your Pokemon then dive into those dark spots by pressing A then look in a few diffrent rooms shards will appear looking like pokeballs so pickup! Every! Pokeball! You! See! I hope this helped!