一般解释

VCC：C=circuit 表示电路的意思, 即接入电路的电压；

VDD：D=device 表示器件的意思, 即器件内部的工作电压； 

VSS：S=series 表示公共连接的意思，通常指电路公共接地端电压。 

GND：在电路里常被定为电压参考基点。 

VEE：负电压供电；场效应管的源极（S）

VPP：编程/擦除电压。 

V*与V*A的区别是：数字与模拟的区别

数字电路供电VCC 
模拟电路供电VCCA
CC与DD的区别是：供电电压与工作电压的区别（通常VCC>VDD）
VDD是指工作电压，就是供电进芯片的 
VDDA是模拟电压或者叫模拟正电源，是从芯片向外供电的

1、对于数字电路来说，VCC是电路的供电电压,VDD是芯片的工作电压（通常Vcc>Vdd），VSS是接地点。 
2、有些IC既有VDD引脚又有VCC引脚，说明这种器件自身带有电压转换功能。 
3、在场效应管（或COMS器件）中，VDD为漏极，VSS为源极，VDD和VSS指的是元件引脚，而不表示供电电压。 

4、一般来说VCC=模拟电源,VDD=数字电源,VSS=数字地,VEE=负电源
5、从电气意义上说，GND分为电源地和信号地。PG是 Power Ground（电源地）的缩写。另一个是 Signal Ground（信号地）。实际上它们可能是连在一起的（不一定是混在一起哦！）。两个名称主要是便于对电路进行分析。 
 进一步说，还有因电路形式不同而必须区分的两种“地”：数字地，模拟地。 
数字地和模拟地都有信号地、电源地两种情况。数字地和模拟地之间，某些电路可以直接连接，有些电路要用电抗器连接，有些电路不可连接。

 

维基百科

下面是维基百科关于电源电源输入的解释

IC power-supply pin

Almost all integrated circuits (ICs) have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the power-supply pins. However, the labeling of the pins varies by IC family and manufacturer.

Typical supply pin labeling
	BJT	FET
Positive supply voltage	VCC/VBB	VDD	V+	VS+
Negative supply voltage	VEE	VSS	V−	VS−
Ground	GND	GND	0	0

The simplest labels are V+ and V−, but internal design and historical traditions have led to a variety of other labels being used. V+ and V− may also refer to the non-inverting (+) and inverting (−) voltage inputs of ICs like op amps.

For power-supplies sometimes one of the supply rails will be referred to as ground (abbreviated "GND") - positive and negative voltages are relative to the ground. In digital electronics, negative voltages are seldom present, and the ground nearly always is the most negative voltage level. In analog electronics (e.g. an audio power amplifier) the ground can be a voltage level between the most positive and most negative voltage level.

While double subscript notation, where subscripted letters denote the difference between two points, uses similar looking placeholders with subscripts, the double letter supply voltage subscript notation is not directly linked (though it may have been an influencing factor).[1][2]

一位网友的解释

来源：all about circuts

what is Vcc, Vss, Vdd & Vee?

They are derived from a more general naming convention.

If you have Va, Vb, or other voltages with a single subscript, then what is meant is the voltage of that node with respect to some reference node. That reference node is "ground" or "common" and is usually just indicated as "GND" or something similar. You are free to pick any node you want as your reference node, but usually one or two nodes are the most reasonable candidates.

If you have Vab or other voltages with two subscripts, then what is meant is the voltage of the first node with respect to the second node or

Vab = Va - Vb

This notation is actually quite useful because it allows you to figure out an unknown voltage step by step.

For instance, let's say that I want to know Vac but I only know Vab and Vbc. Well, I can use the subscipts to tell me that

Vac = Vab + Vbc

This is true because

Vac = Vab + Vbc

Vac = (Va - Vb) + (Vb - Vc) = Va + (-Vb + Vb) - Vc = Va - Vc

So in an expression, I can combine to voltages provided the first subscript on one of them is the same as the second subscript on the other by dropping the common subscript and keeping the other two in their same position.

So Vaf = Vab + Vbc + Vcd + Vdf

So, at this point, what would Vcc or Vee (or any other voltage with a repeated double subscript) be?

Vxx = Vx - Vx = 0V

Since any voltage with a repeated subscript will be 0V, the convention was adopted that a repeated subscript would indicate that the voltage was referring to a supply voltage, usually a DC supply. The letter would generally have some relevance to what the purpose of the supply was.

For BJT circuits, the three common supplies are Vcc, Vee, and Vbb for the collector, emitter, and base voltage supplies. The Vbb is sometimes an actual supply, but more often it is the thevenin equivalent voltage associated with the base bias network. One fine point is that, by general convention, Vcc and Vee are associated with the collector and emitter sides of an NPN transistor. This is commonly, but not universally, the case even if the only transistors in the circuit are PNP transistors. A quick glance at the schematic will tell you if this is the case or not.

For MOSFET circuits, the three common suppies are Vdd, Vss, and Vgg for the drain, sourse and gate supply voltages. The same remarks regarding polarity apply here.

The strict meaning of these has been lost among a growing number of people, and hence you will often see Vcc used as the positive supply in CMOS circuits and see Vdd in BJT circuits.

In many circuits, Vss/Vee is the same as the ground node, in which case it may or may not ever be noted as being Vss or Vee. In other circuits, there may be a more reasonable choice for the ground reference that is, generally, somewhere between the two values making Vss/Vee negative.