Not being an idiot, it's not clear unless you know about them
When (if) you're shooting in JPEG on the D300, you can have the 'Picture Controls' that make your pictures come out differently, you probably already know that. The defaults are 'Standard, Vivid, Neutral,' and another I think. You can edit these to your liking and save them, which is a good idea to get the best out of them.
BUT! Many people also wanted to get something that replicates Velvia film or the others mentioned, and you can
create these custom 'curves' (not actually curves, misleading name), in Capture NX, and save them. This is what these are, people's ready made 'curves' or 'Picture controls' that replicate the best films from 'back in the day'
HTH
