What is Vcc, Vee, Vbb, Vdd and Vss stand for?
If you read a schematic diagram especially the IC pins, you will notice that there are certain pins that we do not really know what it stand for. They are all supply voltages. Vcc = Collector supply voltage, Vee = Emitter supply, Vbb= Base supply voltage, Vdd = Drain supply, Vss = source supply. Whenever the supply to a Transistor (or TTL IC circuit) is connected between the collector and ground it is a standard to notify it as Vcc. If you connect the supply between Base and ground we will call it Vbb and the same goes with Vee for emitter to ground.
Since there is no notion to identify ground (0) this method was simply adopted. The voltages can be negative or positive depending on the the device and the circuit configuration. This method is a standard specified by Institute Of Electrical And Electronics Engineer (IEEE).