A multilingual site is three sites that answer the same question; hreflang is how you tell search engines they are siblings, not duplicates. Each page lists every alternate with its language code — en, hu, de — plus x-default for everyone else.
The rules are strict: every page must link every version including itself, and the links must be symmetric — if the English page claims the Hungarian is its twin, the Hungarian must claim the same back. Get it wrong and Google guesses, which usually means ranking the wrong-language page in the wrong country.
Related terms
Canonical URL
A tag naming the one 'real' address for content reachable at several URLs — so search engines rank the copy you meant, once.
Internationalization (i18n)
Building a product so it can be localized — text, dates, URLs and layouts — rather than retrofitting languages into an English-only shell.
SEO
Search engine optimization — making pages findable, indexable and worth ranking: technical health plus content people actually want.
The bench this belongs to
Web performanceA rebuild that loads on a phone on mobile data, in the country your customers are actually in. Core Web Vitals are the measurement, revenue is the point.
