The Multilingual select module, part of the Internationalization (i18n) package, allows you to define whether content is filtered by language on pages provided by Drupal core. This applies to cases in which multiple nodes are pulled out of the nodes table and displayed together on the page, such as on the default homepage (/node). The module allows you to configure whether or not to filter these pages by the current language. If the Taxonomy translation submodule is also enabled, an option will be available for how taxonomy term pages are filtered.
The module also allows you to exclude the module's language selection handling for certain elements (i.e. views, since views has its own mechanism for language filtering) and for certain paths (i.e. admin pages). You can configure these settings at Configuration > Regional and language > Multilingual settings > Selection.