an alphabetical list of words relating to a specific subject, text, or dialect.
Google uses the rel="alternate" hreflang="x" attributes to serve the correct language or regional URL in Search results. This tag is used when content is translated or targeted to users in a specific region.
Some scenarios where 'hreflang' might be used are as follows:
To indicate to Google that http://fr.example.com/ is the French-language equivalent of the English page, do the following:
In the HTML section of the English website (http://www.example.com/), add the link element pointing to the French version: