Like any other online account, this is what Passpack will know you by. Some other websites call it ausername, screenname, or even nickname -- these are all different words that mean the same thing. Passpack calls it a User ID.
Some people like to use their name. You can use capital letters and spaces if you wish, so your User IDcould be "jacksmith" or "Jack Smith". This is your choice, just remember that Passpack considers these two totally different things.
You can change your User ID whenever you'd like by going to Account > Change User ID from within your Passpack account. If you forget your User ID, it con only be recovered if you have set up an email for your account.
Your User ID must be at least 3 characters longs and it is case sensitive. It is ok to use accented letters, or a letters from a different alphabet.