Physical understanding of a clock cycle
Imagine a square pulse.



There are the 'high' and the 'low' state.

There are also 2 edges. The rising edge(transition from low to high) and the falling edge(transition from high to low).

Some inputs are edge triggered, while some are triggered by the state of input.

You can know that by their symbol.



The above flip flop's clock is edge triggered, denoted by the triangle and activates on rising edge.
The other inputs, S and R, are determined by their state, ie. high and low.



While the above's clock uses the falling edge, denoted by the circle.

So the ticks and tocks are different for each device.