Loads of people here know what meta tags are and how to use them, so if you're one of them, this post probably isn't for you. Sorry
A meta tag is something within your code that helps label your website in a way that the search engines can read your snippets of text and index you wherever possible.
The main meta tags are the Title, Description and Keywords. There are actually a few other meta tags that people look over a lot and those are Robots and Copyright.
Here's a brief overview of the meta titles and how to use them.
Title Meta Tag: The title meta tag is the first line of offense when it comes to increasing your search engine rankings. You'll want to get a keyword into your title so that Google, Yahoo! and Bing will give you a better ranking among the SERPs for that specific keyword.
Description Meta Tag: You can add an optimized snippet of text so the search engines can use it as the very same snippet that shows in the search results. You'll want to get the same keyword in here that you used in the title for the best SEO affect. Now there is no guarantee that the search engines will use the text in your description, but it can't hurt to optimize it
Keywords Tag: The keywords tag is used for where you want to put the keywords your website or page is about. This tag isn't used much for the bigger search engines, but some smaller engines still rely on the keyword tags so you should never leave them out.
Robots Tag: The robots tag is used to show the search engines whether you want your website to be index or noindex. This means that if the search engine spiders do get to your website they will know if you want it indexable or not. If your Robots tag is set to noindex then you will never show up in the search results. If you're running a business and you want online sales, you definitely want your website to be indexable
Copyright: This tag does exactly what you think, it shows that something on your page, or all of it, is copywritten. There aren't too many people who still use this tag, but again, treat it just like the keywords tag and add it in because you don't know what search engines will use it
Post your experience with meta tags and how you use them. I'm sure someone here would love to hear what you have to say