What does the QH' pin do on a shift register?

I am working on a project with shift registers and I would like to know what this pin does. I have heard that it isn't involved with "latching" but I don't know what that means exactly.

"QH" is the serial output for daisy-chaining multiple shift registers.
Leo..

Using the 74hc595 as an example, outputs QA thru QH, represent the 8 bit parallel output of the 8 bits shifted in with QA = bit 0 and QH = bit 7. Normally QH' is used as the daisy chain output to the next shift register.

Check out the shift register data sheets for the timing diagrams explaining this.

Thanks for the response guys! I have also done more research about this! I will definitely be using this forum more often...