Tin - lead solder works well because it melts at a wide temperature range starting at roughly 360°F. Most tin – lead solder has a 60/40 ratio of 60% tin and 40% lead. It is very common and easy to solder, leaving a good strong bond if soldered correctly.
Lead free solder is generally not as well liked as it's properties are not as well known. Tin-silver-copper is the most common makeup of lead free solder. Lead free solder is harder to solder with.
For beginners it is best to start with tin - lead solder as it is easier to solder. Most solder is tin – lead unless specifically labelled lead free solder. See examples of both kinds of solder below with the lead free solder on the left.