You can place these Meta Tags in-between the head tags.
The Content Type tells the browser what to expect. If you don't define this, then the browser will make an educated guess.
All browsers use a "cache" (storage) to keep copies of your website on the visitors computer. This way the browser doesn't have to download the same home page everytime you return to it. The Expires attribute defines for how long a cached page is good.
The Description is often used by search engines as the description of your webpage. Some search engines create their own description, instead.
Search engines once trusted the Keywords and keyphrases which you list. Now they prefer to send robots to read your webpage and figure their own keywords. So, this is rarely useful anymore.
The Language should be self-explanatory. If you don't define this, then then the browser will make an educated guess.
The Robots attribute controls whether search engine robots (called spiders) are allowed to "index a page" (make it part of their search results). The NOINDEX value prevents a page from being indexed, and NOFOLLOW prevents links from being "crawled" (visited by spiders).
Search engines often keep cache copies of popular sites. NOARCHIVE tells a search engine not to store a cached copy of your page.
You can also use Meta Tags to create redirects. See the beginner section of this site.