LSB stands for the least significant bit and MSB stands for the most significant bit.
This circuit is an half adder and it takes the input a and b and adds all the 1s and 0s up and carrys excess 1s over in the truth tables.
We made the half adder more efficient by only using two gates because it cuts down on price and is quicker because it is not going through as many different gates. We can use just one gate for the sum because it matches up with the sum because we have changed just one thing.
A full adder works by three one-bit
A full adder works by three one-bit