 The three most common types of capacitors you're likely to use are ceramic, electrolytic, and tantalum. Ceramic capacitors are non-polarized, so you can place them in the PCB either way. Electrolytic caps are usually polarized. Their negative lead needs to connect to a lower voltage than the positive lead. That negative lead is labeled with minus signs. It's usually connected to ground. Tantalum capacitors are also polarized, but they have their positive side marked. Yes, that's opposite from electrolytic. Tantalum caps are also a lot more sensitive to incorrect installation. If you plug an electrolytic in backwards, it usually just won't work as well. But reverse the polarity and tantalums throw a tantrum. Please do not try this at home. But please do mind your cap's polarity.