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In the previous video we left
the question as to how MVC.

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associated the URL comic books/detail
with our controller action unanswered.

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Let's answer that question now.

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In the URL http://teamtreehouse.com/,

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http is the protocol, and
teamtreehouse.com is the host name.

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Typically, the host name is
the domain name of the website.

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However, when running websites locally,
a special name, localhost is used.

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The number following the colon,
after the host name,

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is our port number,
which in my case is 50153.

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Your port number might be different
as Visual Studio assigns a random

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number when creating ASP.NET projects.

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Using a different explicit port number for
each project allows each to be run locally

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at the same even though they're all
using the same host name local host.

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If the terms URL, Protocol, Host Name or

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Port are unfamiliar to you,
check the teachers notes for

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links to resources that will
explain these concepts in detail.

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The URL, http://localhost:50153/

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would display the default page for
our website.

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Often this page is referred
to as the Home Page.

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For the URL,
http://localhost:50153/ComicBooks/Detail,

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everything to the right of the port
number is known as the Path.

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So while the combination of
the host name and the port number

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is used to determine which website the
request is intended for, the path is used

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to determine which resource within
that website is being requested.

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Whenever MVC processes the request,
it uses simple pattern matching

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against the path to determine
the name of the controller and

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action that should be used in
the form of controller/action.

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So the URL path, ComicBooks/Detail
would map to a controller

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named ComicBooks and
an action method named Detail.

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The process of matching a URL to
a controller action is called url routing.

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URL routing is not unique to Asp.net MVC.

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Many other web frameworks,
both server side and

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client side,
use the concept of URL routing.

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Let's take a closer look at
why we're getting an error

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when requesting our website's home page.

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When making a request,
I'll supply in a path,

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MVC will default the controller name
to home and the action name to index.

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We're getting a 404 error because our
project doesn't contain a controller

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named home controller, let alone
a method on that controller named index.

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If we were to request the URL path comic
books, MVC would successfully find

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our comic books controller but
we'd still get a 404 error because our

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controller currently doesn't contain
an action method named index.

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In a later video,

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we'll add the index action method which
will display a list of comic books.

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We're just scratching the surface
of what URL routing is capable of.

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But for now, these basic concepts
are just what we need to know

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in order to continue
building out our website.

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Our controller's detail action method
currently just returns a string literal.

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Let's see if we can improve upon
that design in the next video.