On a new install, all navigation links begin with 'Directory' and your page titles will be "Directory: Section". You're going to want to customize these to something appropriate for your website. Go to Admin Panel -> Customizations -> Page Titles to set all your page titles. This page allows you to change the titles to existing pages, to new pages you create, and also change the scheme of how titles are organized.

If your site is multilingual, note that you're always editing the titles in your current selected language. Change your language in your profile and come back to the page titles page to edit the titles in a different language.

Advanced user note: You can also set the title of a page within a custom template, by using <!--Area: your title here --> anywhere in the template... however, that method isn't multilingual.