I just bought a condo and its been really cold and snowing today the outside unit is making a really loud noise.. also what does supliment heat mean on thermostat..

You have a heatpump and it is most likely frozen up. Supliment heat would be you're auxiliary heat, switch to that so that the heatpump can thaw out.

For all practical purposes you have two heat sources: a heat pump and supplemental. Since a heat pump performance declines as outdoor temp drops, they are almost always paired with another heat source to well - supplement. It is also called auxiliary heat or emergency heat.

Switch your tstat to supplemental heat to lock out the heat pump from running until you can find the problem.

My unit sometimes gets ice buildup on the fan blade tips, which takes the fan out of balance, and makes a pretty good racket. If its anything other than that you should call a pro.