what is the difference between req.param and req.body method of sending code example

Example: req.params vs req.body

//this is just for me lol
	* req.user: object make by passport.js added to req that include a username and user id
	* req.params: from path segments of URL that match a route definition parameter 
    	* /song/:id
	* req.body: hold parameters sent by post request (like form data)