The search function uses MySQL's full-text search feature. It is designed to ignore search terms that are present in 50% or more of the articles and categories searched. So, the search feature will not return any results until there are a minimum of 3 articles or 3 categories. As your knowledge base grows, the full-text search will produce more and more relevant results, as it will eliminate common terms that are present in many of the articles.

Also keep in mind that the minimum search term length is 4 characters/letters by default. This means that words that are 3 characters or less in length will not work. To change this setting, you must edit your MySQL configuration - contact your web host for more information.