Template:TemplateModuleTreeSimple

mymodule/core/modules/ contains module descriptor file modMyModule.class.php
mymodule/core/triggers contains triggers provided by module
mymodule/admin/ contains pages to setup module
mymodule/class/ contains PHP class files provided by module
mymodule/css contains CSS files provided by module
mymodule/img contains images files provided by module
mymodule/langs/xx_XX contains language files for language xx_XX (try to put at least en_US)
mymodule/lib contains libraries provided and used by module
mymodule/sql contains SQL file provided by module to add new tables or indexes
mymodule/themes/mytheme if module provide its own theme/skin