There is no such thing as "hidden HTTP parameters". You mean probably the HTML <input> elements of type hidden.
Basically, there are 2 ways how browser creates a request with parameters.
1. Using HTML element <form>
In this scenario a web page contains a <form>. This contains <input> elements like text fields, radio buttons, check boxes, buttons. When user clicks on an <input> element of type submit, browser collects all <input> elements in the current <form> and adds them to the target URL, which is defined in the action attribute of the <form> element (assuming we use application/x-www-form-urlencoded). As a part of URL, they are called request parameters.
For instance, if there is a text <input> element with ID "name" and user entered text "John", the browser will append following to the target URL:
or, if there are already other elements:
Some of <input> elements can be hidden. See details here. They behave similar to text fields, i.e. similar to <input> elements of type text, but browser does not display them as fields. That's why they are called hidden. Nevertheless, when user clicks on an <input> element of type submit, not only visible fields, but also hidden fields will be added to the target URL.
2. Using AJAX
Both cases have similarity: Hidden parameter is a parameter that user cannot change via interaction with the web page.