what is an options http request used for code example

Example 1: what is http request made of

1-Http request methods : PUT, POST, DELETE,GET
2-Base URI
3-Resources and Parameters
4-Request Header(which carries metaData)as keyValue pair
5-Request Body

Example 2: options http method

The OPTIONS Method lists down all the 
operations of a web service supports. 
It creates read-only requests to the server.