What is query string?

The query string is a part of URL after the questionmark character.
In URL https://www.bettercoder.com/test/?q=My+query&a=112#abc the quey string is part q=My+query&a=112

• Query string gives the developer option to pass additional parameters in the URL (for example for filtering purposes)
• It doesn't need to be present in a URL at all. In such case the questionmark character is not needed in the URL.
• Query string can contain multiple key-value pairs, where key is name of the parameter and value is its value. The delimiter between key-value is equal character ('='), the delimiter between parameters is ampersand character ('&').