The Apache HTTP Client supports all the commands that are supported by HTTP, such as GET, PUT, POST, DELETE, TRACE, OPTIONS & HEAD.
Most well-known are GET & POST, where GET is used to fetch a resource from the URL and POST is used to store data at a URL. There are official ways in how the different methods should be used, especially when creating a REST API, but in real life most boil down to the GET and the POST.
For a full discussion of the different methods you can read RFC2616 describing the HTTP: http://www.faqs.org/rfcs/rfc2616.html