Module Variations allow for the individual styling of each module within a position, without it being global. Code wise, this is achieved by adding a class into the module code which loads from the Module Class Suffix field in the Module Manager. The theme CSS adjusts accordingly.
Enter any available suffixes at Extensions → Module Manager → Module → Module Class Suffix
There are 4 standard suffixes: icon1, icon2, icon3 & icon4; applicable to the maintop, mainbottom, content-top, content-bottom, footer and sidebar positions.