In dilution streaking a drop of liquid culture is collected with an inoculating loop and then streaked across the agar plate surface. At the end of the streaking the number of organisms clinging to the loop until only single cells are deposited at a given location and you get colony-forming units.
I am wondering now what exactly the purpose of this streak purification is. If you want to grow your bacteria why would you not just put a few drops of the liquid culture on the agar plate? Why is it particularly useful to use this technique? Or, why would you choose this method over the "spread plate" technique, where a liquid culture undergoes a set of dilutions first and each dilution is then placed directly on the surface of separate agar plates.