A 74LS273 is an octal D-flip flop. A flip flop is a digital storage element for a single bit. A "D" flip-flop is a sytle of flipflop (there are other kinds ... JK, T ... the letters refer to the overall architecture of the flop ... in most cases these days, we use D flip flops).

The flip-flop will store the signal on the "input" pin when the clock transitions from a low to high signal (this is referred to as a "rising edge"). After a nanosecond or two of delay, the signal that was on the input pin @ the rising edge of the clock will appear at the "output" pin. The "input" pin can change states, but the output will not change unless a rising edge of the clock signal occurs -AND- the input pin is at a stable state before the rising edge of the clock.

The "clear" signal will drive the output low regardless of the state on the input and the rising edge of the clock.

Make sense? Chances are the "output" pin of the flip flop will drive the circuit that enables a solenoid.

Oh, to be clear, "octal" means that there are 8 flipflops in the chip itself. I don't mean to sound condescending saying that ... some people might interpret that as 8 levels of storage .