An example of a Bronze password.
The Password function in the Golden Sun games is a way to transfer data from the first game to the second. There are three grades of passwords: bronze, silver, and gold.
The Bronze password transfers the characters' names, levels, Djinn collection, utility Psynergy items such as the Orb of Force, and the status of certain events so as to add and influence events in The Lost Age, such as Feizhi giving Felix the Golden Ring if Isaac rescued Hsu in the previous game. You would be just fine with this password only.
The Silver password transfers all of the above plus the exact stats of the original characters, so that stat boosts from items like Power Bread are not lost.
The Gold password transfers all of the above plus the total amount of coins Isaac's party has amassed at the end of Golden Sun and every item in the four character's inventory. The Gold password is obscenely long, weighing in at 260 characters long.
Alternatively, data used in the Game Link cable method is even better than the Gold level password; it transfers all of the above and has all Djinn and equipment actually equipped onto the characters properly (as in, the way they were exactly at the end of Golden Sun). In addition, all Artifacts that were sold back to shops in Golden Sun will now be made available as artifacts in shops in The Lost Age. For players wanting to collect every single item, other than inputting the gold password manually, the Game Link Cable method is the only way to go.