Active low or high only refers to the logic level a control signal is active at. For example, the set and presets of a flip flop might be active low, meaning a low applied to the preset pin will "set" the flip flop and active low applied to the reset resets the flip flop, while a high will do nothing. Or say a chip enable of a memory will be active high, meaning the memory is accessed with a high level is applied to the signal, and applying a low disables the memory.