The page title is defined in the <title> tag in the head of your page:
The title doesn't appear in your page. Don't confuse it with the content titles (H1 title). The page title appears in your browser's tap and in the SERP.
The first goal of your title is to encourage users to click on your title in the SERP of search engines. Your title needs to be creative, attractive and match with your content. Avoid titles with capital letters or special characters.
The perfect length of a title is between 50 and 60 characters.
Choose correctly the keywords in your title. Don't over-optimized your keywords (avoid keywords lists separated with commas). Include the main keyword of your page in your title.
You can find all your title and their optimization in the tab Pages > Content