2 basic solder types: lead free and lead

lead comes in several types: 60/40 (tin/lead) 63/37 (tin lead) 60/37/3 (tin/lead/silver) and some other mixes of tin/lead/silver

lead free: 96/4 (tin/silver) or 100% tin and some other mixes of tin and silver

The difference: (lead vs. lead free solder)
Lead solder pros: flows better, requires less heat, easier to work with
Lead solder cons: LEAD is toxic, lead is a poor conductor (so 40% of your joint has resistance), lead joint is weaker

Lead-free pros: less resistance, much stronger
Lead-free cons: requires more heat and a better iron, doesn't flow as well so flux may be needed

I have used lead-free solder for several years. If you will be soldering and unsoldering the same joint many times, lead solder is better because it is easier to work with. If you use connectors, lead-free solder is better because it is much stronger and has less resistance. DO NOT USE lead solder around small kids, or let them play with your cars. Kids swallow strange things, and if your kid swallows lead solder, IT IS VERY HARMFUL.

If you use lead-free solder, the joint will not be shiny but a dull metal.

They are different and you solder with them slightly differently. Lead solder is already banned in europe, japan, canada, etc, and it is only a matter of time before it is banned in the us.