images - Contain all images related to the theme
infragistics.theme.less - The root file which import all partial files.
Modules - Contain all theme styles related to ignite ui modules.
Styles-guide - In progress theme style guide
framework.less - Contain all styles, that are needed, in order to make ignite UI component's to work properly witch jQueryUI components.
variables.less - Theme variables.
ignite-ui-variables.less -Theme variables.
mixins.less - Contain all mixins related to Ignite UI components

Note: the root file "infragistics-theme-less" is the only file that needs to be compiled to .CSS

Note: The order of File "@import" inside "infragistics.theme.less" is important! In order the theme to work correctly.

File order:

// Bootstrap Theme variables
@import "variables.less";

// Ignite UI Theme variables
@import "ignite-ui-variables";

// Ignite UI Mixins
@import "mixins.less";

//JQuery UI
@import "framework.less";

//Ignite UI styles
@import "modules/modules.less";

// Font styles
@import (css)"icons-styles.css";

Icons web font

*** css/structure/fonts *** hold all files related to icons web font

To add/remove/change icons form the web font:

Go to icomoon.io/app and upload the file "jqurey-ui.svg" located in: css/structure/fonts
Make the desired modification, download and replace the changed font.

IMPORTANT: in order the font to work you need to specify the prefix for the icons clsss. In "icomoon.io", font settings. The prefix should be "ui-icon-". Keep the name for the font the same in order to override the existing font.