Fan-in is defined as the number of input gate has. For example, a two input gate will have a fan-in equal to 2. Fan-out:-
Fan-out is a term that defines the maximum number of digital inputs that the output of a single logic gate can feed. Most transistor-transistor logic (TTL) gates can drive up to 10 other digital gates or devices.
As a result of applied voltage and currents flowing through the logic IC’s, some power will be dissipated in it in the form of heat. The power drawn by an IC from the power supply is given by,
$$P= Vcc X Icc$$
Noise Immunity is the ability of a device or component to operate in the presence of noise disturbance.