The PIN number that you are referring to stands for your Personal Identification Number. It is often times referred to as your IP PIN-which stand for Identity Protection Personal Identification Number.
The PIN is a 6-digit number that you come up with yourself. Essentially it serves the same purpose as your AGI (Adjusted Gross Income) for the IRS. It is a way they can securely look you up, validate you are who you say you are, and look at previous Tax Return information that only they have access to (TurboTax has no access to that information).
Below I have attached a FAQ link that has more information as to what your PIN is:
Going off that, you may not need a PIN, however you might need one as well. It depends on your personal tax situation.
I hope this information provided some clarity for you. Best of luck moving forward!