A Page Title is one of the most important ranking factors for your pages. Your page title tag shows up in Search Engine Result Pages (SERPs), meaning search engines such as Google, Yahoo, and Bing use the title tag as the search results' title for that page.
The purpose of a meta description tag is to provide a short and concise summary of what content is on your website. Search engines often display meta description tags in the Search Engine Result Pages (SERPs), and they serve as an introduction to your web site. Reading that description will probably determine whether a person decides to visit your page or not, so the better your meta description tags are, the better the chance that someone will actually click on your link and visit your website.
Here's a visual of title & description together, in action: