High-EQ people know dozens of words to describe the emotional states of others and theirs; this helps them to manage and control their feelings and not to let their emotions control them. 

Eskimo and Inuit people have dozens—if not hundreds—of ways to describe snow under different conditions.

Advanced chess players know the names of hundreds of variations of different chess openings. 

The minute you give a name to something and make an effort to remember that name, you carve out space in your brain for that concept. You designate a drawer in your intellectual cupboard to that idea. The next time you need to refer to that idea, you know where to look for it.

Referring to unnamed, untagged, and unclassified ideas are as futile as searching for a needle in a haystack. Having an organized storage space matters not only in your physical home but also in your intellectual home.

For that reason, it is not unreasonable that the breadth and depth of one's vocabulary measure at least some dimension of intelligence. The more words you know—the more ideas you understand, the more experiences you've had.

Consider the word epiphany. It's nonreligious definition is:
—A sudden, intuitive perception of or insight into the reality or essential meaning of something, usually initiated by some simple, homely, or commonplace occurrence or experience.

Can you truly understand the word epiphany, unless you've experienced one yourself? No. In the same way, that we cannot understand what coffee tastes like until we've had our first cup.

Learn words. Understand life.