There is it seems a lot of confusion amongst web site owners and people dabbling in occasional SEO as to the value of Titles and Meta Descriptions on their sites. Where many have become confused is where Google no longer use Meta Keywords, though Yahoo and Bing do to some extent.
Titles and Meta Descriptions though are very important to SEO and in two ways. Firstly Google will rank pages higher for a keyword found in the title and meta description, not much higher but a little higher as long as the titles and descriptions don’t seem spammy or stuffed with keywords. Basically Google are interested in showing relevant pages and they know that keywords within a page can be misleading but if they are found in a title and meta description this gives a better indication of what the page is about.
At the same time though the title and meta-description if given are shown in the search results usually in Google. Google will generally use your title and meta description for your result if they contain the keyword someone is searching for, otherwise they may use another snippet from your page though the title is less likely to change.
For you as a webmaster you want to get your site not just showing near the top in Google but want to maximize your chances of it getting clicked upon. As well as more traffic Google now consider your click rate to some extent and so it can improve your rankings for a specific keyword if your result gets clicked more often than those above you.
People generally don’t click blindly they look at titles and the description or snippet in Google results before clicking; they don’t always read it in full and often just look for the results that include the keyword they are looking for, which Google put in bold. So including your main keywords will help get more traffic but there are still a proportion of people who do read titles and descriptions fully so you need to write some information to get them to click, try to include your unique selling points or confirm what your site offers.