There is lots of categories in meta tags like Title tag , Description tag, Keyword Tag, h1, h2 ,h3 tags, Alt tag...All are very important to the SEO point of view..
Well nothing to complicated really. The meta keywords tag, I wouldn't bother with that since all the major search engines do not use it for rankings. It simply informs the search engine of what is your page containing. It doesn't mean that if you don't put a meta keywords tag the search engine won't know what is your page's content. He can figure it out on his own. In the past the meta tag was the main may to get ranked, but people spammed it so much that the SERPs has no relevancy to the queries. Nowadays it is pretty much useless and a waste of time. For the meta description tag, it also has no ranking weight but it is still useful. The description tag is the first description a user will get of your website when you show up as a SERP. So having a relevant and appealing description is quite important. Also including some keywords would be good because they will be highlighted in search results to match the keywords that are in the query. Having an attractive description could increase your click through rate. Try keeping it lower than 160 characters because that is all that will be shown by a search engine. The meta robots tag is used whenever you wish the search engine to do or not to do certain things on your web page. For example if you wish the search engine to follow or not to follow certain links on your web page. If you wish to get indexed or not for that web page. For some search engines, you will have to include their robot name. So we'll use Google as example. Their robot is called "googlebot" and I want Google's search engine to index my page but not follow any links, it would look something like this: <meta name="googlebot" content="index, nofollow"> *There is also a function called "noarchive", search engine's won't archive any information of your website. In other words, you won't appear in search engine's "cached" pages.
You are completely wrong. There is 3 main meta tags and they are the meta description tag, the meta keywords tag, and the meta robots tag. The title tag like you said it is the title tag, it has nothing to do with the meta tags because unlike the meta tags, the title tag has impact on your rankings and carries some weight. h1, h2, h3 are headlines that should be used in your page's content. I don't see how this is part of a meta tag category. For the alt tag, that's just a tag that you should add to your images because search engine's don't have eyes they cannot see images. So you give your a title and an alt tag so the search engine gets an idea of what the image is and if there is relevancy between your content and your images.
Since the search engines use a wide variety of factors to determine site rankings, optimizing a page to rank high is a cumulative effort. You should use everything available to you that the engines might give some weight, and therefore you should certainly use meta tags. Following points is helpful to determine the Meta tags: * Choose your relevant keywords. * Write the site's content based on these keywords. Using H1, H2 and H3 Meta tags properly. * Create a title tag using the same keywords. * Create a meta description tag as a marketing sentence, also based on these keywords. Once you do the above things properly, putting together your meta keyword tag is a very simple procedure. (Though Meta Keywords are not much important now.)
Just try to focus on title and description meta tags others are not that much use full. In title tag you should be writing your most prominent keywords and in description you should elaborate your website.
Mainly there are two meta tags, which are written in header part of web page. They are Meta description and meta keywords.