Learn Spanish (Latin America): El hombre que usa lentes tiene una barba negra. - The man who wears glasses has a black beard.

In Spanish, que is the most common relative pronoun. It can mean "that", "which", or "who". Even though we are talking about a person (el hombre), que is perfectly correct and is actually the most natural choice here to link the ideas. While quien (who) exists, it is mostly used in formal writing or right after a preposition, like con quien (with whom).

I thought usa meant "uses". Why does it translate to "wears" here?

In Spanish, the verb usar (to use) is very commonly used to mean "to wear" when talking about everyday clothing, accessories, makeup, or glasses (lentes). You can also use the verb llevar to mean "to wear", so el hombre que lleva lentes would also be completely correct!

Why isn't there an article before lentes? Shouldn't it be usa unos lentes?

When talking about wearing a general category of clothing or accessories, Spanish often drops the article. Saying usa lentes is just like saying "wears glasses" in English. You only add an article if you are talking about specific glasses, like usa los lentes de sol (he wears the sunglasses).

How do we know which verb belongs to which part of the sentence?