In digital electronics/computer communication 1 or 0 is used to represent all information and is called a bit
Group of 8 bits is called a byte
Nibble is a group of 4 bits
MSB- Most significant bit, this is the leftmost bit of any number
LSB- Least significant bit, this is the rightmost bit of any number
Gray codes differ in only one bit from one code to the other compared to straight binary codes, for example straight binary codes 0000, 0001, 0010, and 0011 represent decimal 0, 1, 2 and 3. The representation for gray would be 0000, 0001, 0011, and 0010 so that only one bit differs from one number to the other.
Gray codes help in simplification of Boolean expression as there is only one bit difference and are widely used in K maps (Karnaugh Maps). They are also called as reflected codes as they can be generated by taking mirror image (reflection)
The digital circuits for which present input decides the output at that instant are called as Combinational circuits, for example an adder or a subtractor circuit. Whereas those digital circuits for which output at any instant depends on present as well as previous inputs are called Sequential circuits, for example counter circuit. Since in sequential circuits the output is dependent upon previous input they have an additional memory element in the circuit.