URL commands are simply the slightly odd domino url structure based on what seemed like a good idea in 1996. They won't do anything unless there is an application (database) on the server that has been built to do what you want.
On a Domino server you will typically find that the database contains all the design elements and logic for the web application. All the code is internal to the database and the developer builds the web application using features of domino, e.g. forms, views, agents etc.
A very simple application for entering data and viewing it may consist of a single form (domino design element, not html form) for entering and viewing documents and a single view for listing the documents that have been created. These design elements would be created in Domino Designer and when the database was put on a server the documents created would also be stored in the same database.
It's possible to interact with the data from an external source using various APIs like the java api, or by interacting with a webservice that the domino application developer has provided.