What is an "international equivalent" in the sentence
What does &quot;international equivalent&quot; to high school refer to?

The typical American university is not going to know if your local school is &quot;good enough&quot; to be equivalent to US high school.  If you have completed whatever schooling is customary before enrolling in a university in your country, then if you claim it is equivalent to US high school you will very likely be believed.  Do plan to provide a document showing you completed whatever schooling, translated as necessary, in case someone asks for it.
While the vast majority of US university students have graduated from high school, plenty of people get university degrees without graduating from high school.  So this is not a question that needs careful thought.