Extension theory for fusion categories

I'll bumble my way through Etingof-Nikshych-Ostrik's explanation of classifying G-graded extensions of fusion categories. Daniel may have to catch me if I fall. Along the way, we may get distracted into related topics such as equivariantisations and de-equivariantisations, and possibly go on to extensions by gadgets other than groups. Generally the theme will be "interactions of groups and fusion categories".