The function of inverters depends on the technology. In digital technology, it is a logic that outputs the output state as a logically inverted input state. In terms of gates, the reversal corresponds to a NOT gate. If the logical input level from a digital logic is a one, then the signal is inverted in the logic circuit and output as a logicalzero.
For analog signals, for example a sinusoidal signal, the phase position of the signal is rotated by 180°. The positive half-wave is output as a negative half-wave, whereby positive levels become negative, and vice versa.