Themes can contain branding information - the name of the application, what logo to show, and the footer.
Use the Theme Brand type to enter this information. Enter the information you want on the Brand tab. All sections are optional - default branding will be applied if you do not enter anything.
Like the theme style, the Advanced tab also contains an Include section. Use this to include components that must ALWAYS be present to support the branding. Typically this is limited to a CSS file that formats the logos, and any styling for the footer.
You can test your branding by installing an assembled theme.