Earlier today the a/c unit tripped the breaker. I reset the breaker but the outside unit will not kick on. Please advise.
Some component has failed in the a/c unit. This act of failing caused the breaker to trip. Now the failed component is preventing the a/c unit form starting.
The unit needs checking to find out which component has failed so it can be replaced. Disconnect the supply and use a multimeter to trace the control path.
The first thing to do is to read your Owner's Manual and see if it has reset instructions. If you have a new-ish unit, there may be error codes displayed on a control panel inside the compressor housing (or on the thermostat panel if there is a display there).
And it should go without saying, but: check to be sure no debris is jamming the fan, that there are no obvious signs of broken tubing, scorch marks from burnt components, etc.