Jjok-pa is a small thin green onion that has a bulb on the end. It is a spliced breed of green onion and onion and that is why it has its differentiating bulb. The bulb on the end is how it is differentiated from Sil-pa (실파), which is another type of thin green onion that looks similar to Jjok-pa. Jjok-pa is used to make kimchi and pancakes.
Before using Jjok-pa, soak it for 5 minutes in vinegar water to remove the dirt, and then remove the root and peel off the outside layer from the base of the green onion to reveal a clean under layer. You can also purchase it already cleaned (Kkan-jjok-pa (깐쪽파) is the name of the already cleaned version, but it may be hard to find this cleaned version in America.)
Sil-pa (실파)
Kkan-jjok-pa (깐쪽파)