Styles - Change your typeface, font colours and general site colours.
Layouts - Choose between different layouts for your home page, portfolio, projects and blog.
Settings - Adjust all the settings for your theme such as page counts and crop ratio.
Once inside the Theme Layouts tab you will see all that available layouts for each section of you site. On some of the layouts you might see a palette icon like so:
Click the palette icon to reveal the options for that layout. In the options area change anything click Save and those changes will only effect the pages using that layout.