Why Tess?

I learned about the Tess.design AI generator from a Reddit post, when I did a search for "ethical AI." I am writing this page after experimenting off and on for one week. 

I paid $20 for a monthly subscription, which allows me to do 40 generations. Exactly what constitutes a generation is unclear. Tess is fairly new,  and although the steps to USE the generator are fairly simple and intuitive, I have not found good reference materials for questions such as what constitutes a generation?