I would guess that you have roundwound strings, because that is the most common. Some are stainless
steel and some are nickel (with a stainless steel core). Nickel is newer and in like the 70s all strings were stainless steel. Nickel is however a softer metal so it is easier on your fingers and frets, but it does not sound as 'bright'. "102" would be the guage, or the thickness, of the string, that is .102 inches (correct me if I am wrong, I am used to the metric system but that seems about right

). Anyway, I have never seen gauge 102 so you probably got 105. That is considered medium gauge. Therefore, buy roundwound strings, nickel or stainless steel, in medium gauges, that is 45-65-85-105 or 45-65-80-105. Get one of the cheaper sets at your local music store and see how you like them. There, I think I have explained it pretty well.
