Title tags are usually used by search engines to determine the subject of a particular page and display it in SERPs.
<title>Your Fantastic Title</title>
Meta description is a short paragraph of text in the HTML section of a page. It is usually displayed in a SERP snippet after website's title and URL.
<meta name="description" content="Your gorgeous description">
Open Graph (OG) tags meta tags in HTML section of a page that allow any webpage to become a rich object in social networks.
<meta property="og:title" content="The Rock" />
<meta property="og:type" content="website" />
<meta property="og:url" content="http://www.imdb.com/title/tt0117500/" />
<meta property="og:image" content="http://ia.media-imdb.com/images/rock.jpg" />
<meta name="robots" content="index, follow">
When you have a few pages with identical content, you can use a canonical tag to tell search engines which page should be prioritized.
<link href="URL" rel="canonical">