To "pulse" a parameter is to send it a signal from (1) an exported CHOP channel or (2) a python command or (3) a mouse click that causes a new action to occur immediately.

Some parameters are specifically Pulse-type parameters such as Reset Pulse in a Speed CHOP. You can create custom Pulse-type parameters in the Component Editor.

A pulse via python is via the .pulse() function on a pulse-type parameter, for example op('speed1').par.resetpulse.pulse()

TIP: The benefit of the Pulse parameters on timed things in TouchDesigner is they act immediately - Speed CHOP's Reset pulses and Cue pulses on Movie File In TOP etc often have a on-off toggle plus a Pulse parameter. For the on-off toggle, while they are on, even for 1 frame, it's frozen in a cued/reset state. It's better to pulse the Pulse parameter with something like op('speed1').par.resetpulse.pulse(), which starts counting up on the frame that it's pulsed.

A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel exported to the Pulse-type parameter.

You can also pulse a Pulse-type parameter using an expression in the parameter that goes from 0 to 1 to 0.