The Path translation module, part of the Internationalization (i18n) package, allows you to map together existing pages that are translations of each other. This will allow users to use the language switcher to navigate between the associated pages.
The module is meant to be used as a last resort to translate paths that can't otherwise be mapped together as translations. For example, paths to translated nodes can already be linked with the Content translation module and paths to translated taxonomy terms can be linked with the Taxonomy translation module. Path translations should be used to link generic paths, such as those provided by Views or Panels.
To set up translations of a particular path, you need to create a path translation set by going to Configuration > Regional and language > Translation sets > Paths and clicking Add path translation.