If you read the book you lifted the image from, you'll find the items defined in section 1.6.1 and 1.6.2. VDD is the same as \$V_{\text {DD}}\$ and like wise with VOH and \$V_{\text {OH}}\$, which may be confusing you.
1.6.1 Supply Voltage Suppose the lowest voltage in the system is 0 V, also called ground or GND. The highest voltage in the system comes
from the power supply and is usually called VDD. In 1970’s and 1980’s
technology, VDD was generally 5 V. As chips have progressed to smaller
transistors, VDD has dropped to 3.3 V,
2.5 V, 1.8 V, 1.5 V, 1.2 V, or even lower to save power and avoid overloading the transistors.
1.6.2 Logic Levels The mapping of a continuous variable onto a discrete binary variable is done by defining logic levels, as shown in
Figure 1.23. The first gate is called the driver and the second gate
is called the receiver. The output of the driver is connected to the
input of the receiver. The driver produces a LOW (0) output in the
range of 0 to VOL or a HIGH (1) output in the range of VOH to VDD· If
the receiver gets an input in the range of 0 to VIL, it will consider
the input to be LOW. If the receiver gets an input in the range of VIH
to VDD, it will consider the input to be HIGH. If, for some reason
such as noise or faulty components, the receiver’s input should fall
in the forbidden zone between VIL and VIH, the behavior of the gate is
unpredictable. VOH,VOL, VIH, and VIL are called the output and input
high and low logic levels.
When looking at noise margins Voh is the minimum output voltage of an output when high (and typically when sinking some current). Vih is the minimum input voltage that is guaranteed to be interpreted as 'high'. Similarly for Vol and Vil, which are maximum output and input voltages respectively- with a current being sourced.
Here is a typical CMOS gate datasheet showing those numbers. In this case
'Vcc' is used rather than 'Vdd' for historical reasons, but it means the same thing.
CC was used for Collector supply (NPN and positive supply assumed assumed) and DD was used for Drain supply.
74xx chips were originally bipolar, hence the Vcc.
Since most chips are CMOS these days the Vdd supply actually goes to the source of P-channel MOSFETs but never mind about that. You'll also see Vss and Vee, generally used to refer to GND and negative supply respectively. You may even find chips that have something like Vee = -4.5V and Vcc = GND (ECL logic chips).
