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To get a sense of what the rest API
is let's first talk about rest.

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Rest stands for
representational state transfer and

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is a way of defining how a web
server should respond to requests.

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Normally when humans interact with
the Internet they use a web browser

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as a client.

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The browser makes a request to
the server and HTML and CSS is returned.

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It's human friendly.

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Machines can also make requests
to URLs and ask for resources.

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These responses are intended for
machines, not humans, so

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no HTML and CSS are returned.

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This type of response is
normally formatted in JSON.

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A good example of this is
the Twitter app on your phone,

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it makes a request to Twitter's rest API
to get the tweets before you see them.

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The JSON from Twitter's API is then
formatted and displayed on your phone.

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API is done only allow you to read data
but also add update and delete data.

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Each of these actions can be mapped
to an HTTP verb post, put or delete.

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By combining an HTTP verb with
a URL an API can do many things.

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Such as post tweets,
delete emails or even transfer money.

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When a set of URLs are designed to
interface with a back end program in this

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way we call it a Rest API, or
application programming interface.

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Let's look at the demo user interface for
our Rest API again.

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I'll open up the Chrome developer tools
and then click on the network tab.

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This will allow us to see what's
happening when we use our user interface.

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When we submitted new
question like why is the sky

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blue, our UI makes an http post
request to the URL slash questions.

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This is via an AJAX call.

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The server responds by inserting
a new question into the database and

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returning it back so it can be displayed.

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When we brought an answer up

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The UI posts a request to the URL pattern.

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Questions, question ID,
answers, answer ID, vote-up.

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The seven responds by increment in
the specified and says vote counts and

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returning the whole question
back with it's answers.

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The UI can now be updated.

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Now that we have a sense
of what a Rest API is and

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how it works, let's plan the API
we want to build the next.