That’s a very vague suggestion, @AnnaPaguia - and a dangerous one, too. Many so-called SEO tutorials are very out-of-date and advocate methods which have long since ceased to be effective and may even result in your site being penalised. The age of the tutorial is no guide; I have seen recent articles which still offer bad advice.
Online tutorials may be good, but accept everything with caution, and always check with the search engines’ guidelines to ensure the advice you take is sound.