>> Hey.

>> I got those burgers we ordered from the restaurant.

>> Awesome, they look great.

>> Looks awesome.

>> I'm going to dig in here.

Wait a second, this doesn't look like a Hawaiian burger.

Where's my runny egg?

>> Yeah and they kind of got the wrong bun on mine, didn't they?

>> Dude, but did you tell them what kind of burgers we ordered?

No, I just called and said, I'd like two burgers to go, please.

And they said it'd be ready in 15 minutes.

>> Dude, really?

You gotta be more specific.

>> I figured they'd just know.

We get the same thing every time.

Maybe I should've told them who I was when I was ordering.

>> Yeah, you think?

Making an HTTP request is like ordering a burger at a restaurant.

If you don't specifically order the cheeseburger medium rare with a fried

egg, you might get a turkey burger on sourdough instead.

>> Yeah, HTTP requests likewise specify explicitly what content you're

looking for and how you'd like it delivered.

>> In this next lesson, we'll talk about how HTTP requests are used to get

the information that we need over the web.

>> HTTP requests are a basic part of how devices get information from other

computers on the Internet.

The idea is you ask for some information, you get a response, and

then you extract the information in a way that's useful.

Every time you visit a page like Google.com on your computer

the web browser sends an HTP request to the address that you entered.

It gets received by the computers on the Internet that Google owns,

which process the request and create a response to send back to your device.

Then the browser on your device interprets the response and

updates the screen, which is the Google home page that you probably recognize.

Now check this out, I'm going to give you a little sneak peak into some neat

developer tools in the Chrome web browser.

Feel free to try this out on your own.

To access Chrome's developer tools, I'm going to activate contacts menu.

That's a right-click usually, chose Inspect.

Now you can see Chrome developer tools has a lot of information about each page

and how it's drawn.

It's got HTML CSS and this stuff here, the Elements tab.

What we want is the Network tab,

the Network tab is going to show us what loaded to create the webpage.

There is a lot of different resources and

we'll see HTML, CSS, JavaScript and images and

that sort of thing all getting loaded into the page at the same time.

So let me do a refresh on this page, and

you can see all this files just loaded themselves.

You can even see the timeline here of how long it took for each one to load.

If I scroll up you can see here's the main google.com resource that we got

with use to get method, to retrieve the page and the status response was 200.

And it even tells us the size and how long it took to retrieve the page.

And if I resize this window a bit so I can see the content down here,

I can even see the request headers that made up the request that came from my

device and was sent to the Google servers.

Now the same communication and transfer happens when you request data on

a mobile device whether it's the web browser app viewing a website or

any other app using an API.

Apps can fetch data from some remote source across the Internet,

such as computers owned by the USGS.

Let's explore HTTP in a little more detail.

When we make an HTTP request, we're basically including very specific

directions on what information we want from another computer on a network.

In the request we include a uniform resource olcator or

URL which is the address or location of the data source that we want.

The URL tells us that we need to communicate with computers at USGS as

opposed to the computers at Google or any other organization.

A URL should look pretty familiar to you.

It's a string of characters you type into your web browser whenever you want

to visit a web page like google.com or udacity.com.

Let's take a look at this example URL.

The first part is called the protocol or scheme.

This is usually going to be http or https.

The next part is called the host, domain, or authority.

These all pretty much mean the same thing, the main identity of the web

resource you're connecting to like udacity.com or google.com.

The next part is the resource path.

This is analogous to a file or folder structure on your computer, or

some other hierarchical organization of information.

The final part is called the query.

The begin of the query is indicated by the question mark.

The query is an optional way to include information about things you're looking

for like search terms or categories of information.