Does anyone know if I can buy a TIM or Wind sim card at FCO?

anyone ???

Yes, there's a TIM store in the terminal on the second level. I always go there to buy one before I go into Rome, or to get my rental car.

What is a TIM or Wind sim card?

AT&T and T Mobile cell phones in the US and all cell phones in Europe use gsm technology. For cell phones of this type a small chip known as a sim card is needed to connect to the service provider and thus to make and receive calls. To my best knowledge all sim cards are inserted into a slot underneath the battery. If you have a gsm phone, and if it is unlocked (works with any service provider), and if it operates on the European freequencies, 900 and 1800 mhz, then you can use it in Europe with either a local sim card, valid for a particular country, or an international sim card, which can be used in many countries. Many people like local sim cards because the call rates are cheaper than for international sim cards. Tim and Wind are local Italian service providers. International sim cards are discussed in a number of threads in this forum.