The black is usually hot all the time, the red would be a switch leg, ie hot only when the switch is activated. If you have a ceiling box with red, black and white, it was probably wired for ceiling fan installation. The black would be for the fan so it could run any time and the red for switching the lite on/off. For chandlier you will probably use the red and white, the black you will have to cap with wire nut to make it safe. Suggestion: Buy a voltage sensor @ local hardware store, they are cheap $12-15, you can use to test my circuit theory, also test circuit and turn off before working on it. Never work a hot circuit. Good luck, remember electricity kills you dead.