When you're in the Help Center, you'll notice a Search field on the top of every page. All of our articles are tagged with keywords, so that common search terms will find the article.
It's important to know how the Zendesk search works, though.
If you type in the search box at the top of an article, it's going to look for those terms in that article. In the screenshot below, the search for "stripe" within the article yielded no results.
On a category or section page, it's searching for that term within that category or section. In the screenshot below, the search for "stripe" was entered at the category level, and yielded 3 results.
On the main (home) page, the search is going to look for the term in every article posted. You'll get the most results here, without wondering how the article was categorized. The screenshot below shows the same search from the home page, and it yielded 7 results.