an alphabetical list of words relating to a specific subject, text, or dialect.
When you have websites in same language but for different markets or different language for the same or different markets, you can pass this information on to Google using hreflang tags.
Using the hreflang tag will enable Google to showcase the right page to the right audience.
The hreflang is a link attribute used as (rel="alternate" hreflang="xxYY"), where xx is the language (ISOxxx standard and link) and YY is the 2 letter code for country. (ISO yyyy standard and link)
You should use this tag if:
• You use translated content (similar real life example)
• You have content with minor variations (currency, NAP information)
How to implement hreflang?
Say you have three websites, each targeted to UK, US – English and US - Spanish. Any page of such a website should have the following set of hreflang tags.
• Link 1
• Link 2
• Link 3
For searchers outside your given hreflang tag, you can provide a default option with following :
HREF lang tag implementation
HREF Lang tag is specified in 3 different ways:
2. XML Sitemaps
3. HTTP Headers
If you have pages in multiple languages, all language page must contain hreflang tag. All pages must also point to itself.
Benefits of HREF Lang
• Help create localized content optimized for users language and location help in improving user experience
• Hreflang saves from duplicate content issue
Find more here : https://yoast.com/hreflang-ultimate-guide/#hreflang-seo-benefit