Uniform Resource Locator (URL)

In order to get anywhere on the web, we need to know the location of of the document, or resource, we want to retrieve. This is specified by a URL:

             hostname
            ┌───┴────┐
    https://reddit.com/r/gifs
    └─┬─┘             └──┬──┘
    scheme              path

Source

A URL can be broken down into the following parts:

• scheme - The scheme helps us to determine the protocol which we will use to make a request. In this case, HTTP Secure. Some other schemes we could use here are ftp, mailto, or news.
• hostname - The name which is used to identify the Host, or server of the information we wish to retrieve. Behind the scenes, this hostname must be translated to an IP address. DNS servers handle this process.
• path - This indicates to the server the resource we wish to retrieve.

URL Fragments

                hostname                              fragment
            ┌───────┴──────┐                         ┌───┴───┐
    https://en.wikipedia.org/wiki/Fragment_identifier#Examples
    └─┬─┘                   └───────────┬───────────┘
    scheme                            path

Fragments allow us to jump to an id within a document. This is useful when the information you want someone to view is a few pages down within a HTML document. Try visiting the above URL in your browser.

More on fragments, here

URL Query String Parameters

Consider this example URL generated when performing a search via Google.

             hostname          query string
            ┌───┴────┐       ┌──────┴───────┐
    https://google.com/search?q=cats&tbm=isch
    └─┬─┘             └──┬──┘
    scheme              path

The query string, aka params, is a series of key/value pairs, which allows the client to pass some information to the server. In many cases, this information is usually provided by the user by submitting a form. In this specific case, the query string indicates that we have performed an image search for cats.

key	value
q (query)	cats
tbm (type of search)	isch (image search)

More on query string parameters, here