Simply explained, Meta Tags are part of the HTML code of a web page that imparts information about the siad web page to web browsers such as, Explorer and Firefox, as well as to search engines.
If you are building a website or own a website the three really important Meta Tags that will help get your website found are, the Meta Page Title, Keywords and the Meta Description.
The Meta Page Title appears in the bar at the top of a browser window, in the case of Microsoft Explorer it is the text that appears immediately before the wording in the blue bar which says Microsoft Explorer. Most search engines place a lot of importance on this title when ranking web pages, so you should ensure that you have a unique title for each of your web pages and they that it contains your top search phrase for that page.
The Meta Description, is as it sounds, a description of what that particular web page is about. It is also the text that many search engines use to describe your web page in their search results. Again this is an important Tag that can help get your website found. Like the Title Tag most search engines do read these descriptions and put a lot of importance on them.
Meta Descriptions should also be written with real people in mind, as a well written Meta Description can attract people to click on your site when faced with dozens of listings on a results page, even if you are listed towards the bottom of a page.
The Keyword Tag started life as the place to put all the phrases that you wanted your website to be found by, however many website owners found that they could out smart the search engines using them, most search engines no longer pay much attention to them. However some do use them and most will check to see if they have been included, so it is important to use them.
Most web users type in phrases into search engines rather than single words, so you are best advised to use key phrases rather than single words. If you are in a very competitive area you many also want to consider using common mis-spellings as away of avoiding the competition but still attract a reasonable amount of traffic to your site.
Having said all of the above, unless you write web pages about the things you want to get found for the above advice is of limited help.