A 3S1P and a 3S are the same thing - 3 cells wired in series. We've gotten lazy and just don't write th 1P too much anymore.

For charging, the C rate is the batt capacity /1000, so this one would have a 1C charge rate of 5amps. A 2C charge rate is 2 x 5 = 10amps, 3C is 15amps and so on. The higher the C rate, the shorter the charge time. You can charge up to the recommended C rate, but you don't have to charge at max C rate if you don't want to and or have a charger that can't handle the rate.