Frequency refers to how quickly something is cycling, and the Hertz (Hz) unit means specifically "cycles per second."
A cycle just refers to any repetitive motion, relative to some arbitrary reference point. The cycle is complete when the object in reference is at the same point moving the same way when it started.
A trip from my house to work and back is one cycle, but the cycle is not 8 hours because I don't go immediately back to work as soon as I get home. Instead, the cycle is actually 24 hours, because I'm not at my house moving toward work again until the next morning.
You could also look at a tire turning relative to a mark on the ground, or you could look at a weld rod relative to a butt joint. The weld rod completes one weave cycle when it starts, goes all the way to one side, goes all the way to the other side, then returns to where it started.
Now, the frequency in Hertz (Hz) indicates how many times per second the weld rod is going to do this. If you want a fast back-and-forth with less material deposited, you would want a higher frequency. If you want a slower back and forth with more material deposited, you want a lower frequency.
I'm not sure how your welder is configured, but if it's possible to set it to zero that would also disable the weave function because you are indicating that you want the weld rod to go back and forth "zero times per second."
I hope this gives you a better conceptual understanding of frequency!