Search intent (or user intent) is the goal behind a search. It's usually grouped into four kinds: informational (learn something), commercial (compare options), transactional (buy or sign up) and navigational (find a specific site).
Why it matters
Google ranks pages that match the intent. A product page rarely ranks for "how to clean a coffee grinder", and a long guide rarely ranks for "buy coffee grinder". Matching intent is often the difference between page one and page five.
Example
"Best coffee subscription" is commercial: people want a comparison. The pages that rank are roundups and reviews, so a single product page will struggle while a fair comparison can win.
What to do
Search the keyword yourself and look at what ranks. If the top results are guides, write a guide; if they're comparisons, write a comparison. Then make yours more useful than what's there.