Truth table
Beginner
A list of every possible combination of inputs and what the output is for each one.
Novice
A table with one row per input combination ( rows for inputs) and the output value in the last column. It fully defines what a logic gate does.
Expert
The complete specification of a combinational function. For a CMOS gate, each row also tells you which network conducts, which is useful when reasoning about leakage states and worst-case delay.
Explained in CMOS logic (Transistors).