# Internet Fundamentals/Web browsers
## Web browsers
### What is a Web browser?

* A Web browser is an application that displays Webpages.

### Main functions of a Web browser

* Retrieval : the process of bringing information to the user.
* Display : the process of showing information to the user.
* Navigation : the process of moving around a Website in order to access other information.

### Graphical User Interface (GUI) elements of a Web browser

* Navigation buttons : back, forward, refresh, stop, and home buttons.
** The back button retrieves the previous Web page that referred to the Web page currently viewed.
** The forward button retrieves to the forward Web page and only works if the back button has been previously used.
** The refresh button reloads the Web page that is currently viewed.
** The stop button stops a Web page from loading.
** The home button retrieves the default Web page.
* Address bar : a text field used to input the URL of a Website and display this Website.
* Search bar : a text field used to input terms and display several Websites.
* Status bar : a bar that displays information on the URLs of links and information on the Webpage as it loads.

### Main features of a Web browser

* Tabbed browsing : a form of navigation that allows to have multiple Webpages open at the same time.
* Bookmarks : saved shortcuts that direct to specific Webpages.
* Browsing history : the list of Webpages a user has visited recently.
* Page zooming : the ability to reduce or enlarge the content of a Webpage.
* Downloading : the process of copying data from one device to another.

### Main browser extensions

* Plug-in : an application that adds a specific feature to a program.
** Adobe Flash Player : an application that allows the user to display multimedia on Web browsers.
** Adobe Acrobat Reader : an application that allows the user to display Portable Document Format (PDF) files on a Web browser.
** Microsoft Silverlight : an application that allows a user to use video sites on a Web browser.
* Pop-up blocker : a program that prevents pop-up windows from appearing on a Website.
** A pop-up is an online advertising that uses a new window for display.
* Browser cache : a temporary storage of Web data.
** The main purpose of a browser cache is to speed up Internet surfing by saving Web data, so that when the user tries to go back to recently visited Web pages, the browser displays them instead of downloading them again.
* Cookies : small pieces of data exchanged between the Web browser and the Web server that store information about the user.
** The main purpose of a cookie is to identify the user, prepare custom Web pages and save site login information in order to provide recommendations for the user.

## Hyperlinks
### What is a hyperlink?

* A hyperlink is an element that links either to another place in the same document, or to another document.

### Colors of hyperlinks

* Blue : unvisited link.
* Purple : visited link.
* Red : active link.

### Types of hyperlinks

* Internal : links to a different page in the same Website.
* External : links to another Website.
* Relative : links to a specific place in the same page.

## Uniform Resource Locators (URLs)
### What is a Uniform Resource Locator (URL)?

* A Uniform Resource Locator (URL) is a unique identifier used to locate a resource on the Internet.

### Protocol

* The protocol of a URL determines how data is transferred between the host and a client.

### Hostname

* The hostname identifies the host that holds the resource.
* The subdomain identifies the location of the resource on the Web server.
* The domain name identifies the name of the Website.
* The Top-Level-Domain (TLD) identifies the Website geographical area, or the organization that owns it.

### Path

* The path identifies the specific resource in the host that the client wants to access.

### Query string

* The query string assigns values to specified parameters that the resource can use.

### Anchor

* The anchor identifies the specific location of the resource within a page of the Website.