Magento_GoogleOptimizer module implements functionality of Google Experiment tool that is the part of Google Analytics functionality.
Google Experiment (on Google side) allows to make two variants of the same page and compare their popularity. From Magento side, code generated by Google should be saved and displayed on a particular page. Google Experiment functionality is available on pages of products, categories and cms pages. This allows to save different codes for products and categories on different store views. This functionality can be switched on and off on the configuration page (Stores -> Configuration -> Sales -> Google Api -> Google Analytics). Also this functionality depends on Google Analytics module and configuration options.