i have a rank 1 cooking, whats it do exactly?

also herring and cod fish have the same life as sardine? some1 explain please

Rank 1 cooking means you can cook sardines more efficiently and regularly, and you might be able to cook herrings.

Sardine's cap for life/mana is 50, herring's is 100, cod is 150, and so on.

Some background on cooking -- http://ladderslasher.d2jsp.org/index.php?g=7#Cooking

at rank one, you wont be able to cook sardines for prof. you will have to cook herring instead