Please explain the concept list variable in the Colab file

RE: Dreambooth Stable Diffusion notebook

The colab files contains a “concepts_list” dictionary with 4 values: instance_prompt,
class_prompt, instance_data_dir, and class_data_dir. What are these for? Let’s say my
20 images are in /content/data/myimages. what is the meaning of zwx or ukj in the example notebook ?