Titles on an internet site are for the orientation or the reader or visitor. You are therefore in the truest sense of the word outstanding importance, when it comes to the interest of potential customers. Search engines also use this importance, if they analyze heading tags as one of several criteria in evaluating a site. So-called bots take this on. Title tags - including headline tags or short h-tags - are in HTML-format, using six different font sizes - from H1 to H6, depending on the importance of the headline - and are evaluated higher in some search engines than the text itself. You shouldn't use all the six font sizes, as, on the one hand, the headlines would be over weighted in relation to the actual content, and on the other hand there is the risk, that the distribution of the font sizes on the page might be improper.