Why would the in-house fan come on and the AC compressor sounds like it wants to kick on but it just hums?

Does the outdoor fan come on? If it does not, then the fan motor or the capacitor is bad. Does the outdoor coil get hot? How loud is the hum? If the Condenser fan(outside Fan) is running and the condensor is not obstructed by debris or some other object, I would suspect rotor lock. This can be caused by high head pressure. A common cause of high head pressure would be a bad equalizer/unloader valve. This valve is responsible for bleeding the high pressure down during the compressor rest period between cooling cycles. Of course the worst scenario of all would be a siezed compressor. One way to test for a failed unloader or equalizer valve would be to shut the unit off for at least an hour and then restart. If it does restart odds are the valve is bad and not the compressor.