Theme settings are a way to customize the look and feel of Bloom front end apps(alternate wording?) to better match your online store. Through settings, you can change the color of elements like the text, buttons, background, and more. You can also change the base font size. Along with style settings, you can update the content on your online store. Content can be edited in a few different places across the app, typically in the context of what you're editing. 

Edit theme settings

Theme colors and fonts 

Tier content 

Release content