There are four entities that determine the language of the labels and settings in the system:

User settings

All users have a default and an active language - the default language is set up on their user profile and the active language is decided by the course settings. 

Course settings

You specify a language for a course on the Main tab of the Course Editor. In addition, you can choose to override the user's language settings (on the Settings tab) which means that if the course is in a different language from the user's default language, the user sees the language of the course.

Browser language

If specified in the installation setup, the users' language settings specified by their browser setup determines the language of the program and this overrides the user language and the course language in the system. 

Installation setup

You can also specify language settings on the installation by selecting to ignore the browser language. If you do not select the Use user's language settings under Ignore browser language, the language of the browser overrides the settings of the course and the user, and the language versioned labels will be displayed. If you select this checkbox, the active language (coming either from the user or the course) will be displayed and the language of the browser is ignored.