A western style Japanese knife is double-beveled, as other knives (that we're used to) are. Traditional Japanese knives are single-beveled.
A Japanese chef's knife is a gyuto, that is, a gyuto is the equivalent of a typical chef's knife. That's what you want, not the santoku, which is for some reason the one that has made it into mainstream. A santoku doesn't lend itself to the rocking motion when cutting.
A petty (aka "fruit", "utility" knife) is also nice to have. It's basically a paring knife.