It's practically just food for Pokemon that you can make using berries. You can mix the various berries in a Pokemon center.
Regular BERRIES. (Oran Berries in HeartGold).
i think 20 berries
Dingle Berries
oran berries
No, you can't buy berries in Pokémon Diamond.
poffins and berries
To get free berries on Pokemon Pearl, you pick berries you find around the region, plant them, and then pick them again when they are finished growing. With these, you can start the cycle again.
No. But some people give you berries and you can pick/plant them
No, but you can feed them to your Pokemon.
no berries
In Pokemon Gold, Silver and Crystal you need to feel seven berries to the Milktank in Moo Moo Farm. The kinds of berries don't matter. But in the remakes Pokemon HeartGold and SoulSilver the berries fed to it need to be Oran Berries.