Hreflang is an HTML markup that is used when you have pages in multiple languages and/or regions that are similar in meaning. So essentially just translated versions of the same page. This is very important for international SEO.
Using Hreflang on page or in your sitemaps will give you the ability to specifically tell search engines the audience the page is targeting.
- A page for the region, US and in the English language.
- A page in Spanish but also targeting the US region.
- Or English and for the UK.
Google offers help with how to manage multi-regional and multilingual sites in its Search Console help pages.