What in the world is a collocation?

“Learn collocations! Don't learn words in isolation. Look for collocations. Collocations!” What in the world is a collocation? Why are teachers online always talking about them? Are they the key to fluency in English?
I always like to start at the very beginning—the etymology (the origin of words). The term collocation comes from Latin and means “placing together.” Imagine placing a dish on a table. It just makes sense, right? Sure, some days you might eat off a plate on the couch, but generally, plates go on tables and are used with silverware.
Language works the same way. Certain words naturally go together. When they do, we say they collocate.
For example:
“Make a mistake” (not “do a mistake”)
“Heavy rain” (not “strong rain”)
“Fast food” (not “quick food”)
These combinations aren't random. They’re entrenched patterns, deeply familiar and frequently used by fluent speakers, often without conscious thought. This is where cognitive linguistics offers a helpful lens. From this perspective, collocations aren’t just memorized word pairs: they’re meaningful constructions that reflect how we experience the world. For the very inquisitive learner (I’m raising both hands!), this is good news! What this view suggests is that collocations are a result of metaphors or mental imagery that we use to make sense of the world. I know, this sounds a little too crazy… let’s take a look at a few examples.