Merriam-Webster's dictionary defines a web browser as a computer program used for accessing sites or information on a network (as the World Wide Web).
Wikipedia says, a web browser is a software application which enables a user to display and interact with text, images, videos, music and other information typically located on a Web page at a website on the World Wide Web or a local area network.
Some of the Web browsers available for personal computers include Internet Explorer, Mozilla Firefox, Safari, and Opera in order of descending popularity.
All Web browsers are capable of certain basic tasks, like finding and loading new Web pages, and displaying them following HTML standards and conventions.
Web browsers consist of client software that runs on your computer and displays home pages on the Web. There are clients for a wide variety of devices, including Windows, Macintosh, and Unix computers.
Web browsers communicate with Web servers primarily using HTTP (hypertext transfer protocol) to fetch webpages. HTTP allows Web browsers to submit information to Web servers as well as fetch Web pages from them.
When a web browser talks to a web server, it uses something called a universal remote locator (URL). The web address, or URL (Uniform Resource Locator), that you type into the browser's address bar tells the browser where to obtain a page from.
When a user enters a URL into the browser and presses the enter key, the web browser looks at the prefix before the colon and determines what protocol to use. It then looks at the text after the colon to figure out what server to communicate with.
Every server on the Internet has a unique IP Address. The Web browser then requests that the Domain Name Server (DNS) locate the required website. The browser accepts from the DNS (or host server), via the file transfer protocol (FTP), the website information; and then transfers this information to the user's computer. Next the browser evaluates the system requirements, of the user's computer, to determine if it is compliant with the information from host server. The browser then uses HTML to displays the Web page (images and/or text) onto the screen for the Internet user to view.
For example, you typed the following URL into the browser's address bar: http://www.universalteacherpublications.com/java/ebooks.htm
In this case, you're attempting to reach the Java section of universalteacherpublications.com. The browser looks at this particular URL in two main sections. The first is the protocol, which is "http://" then the browser will know that it is talking to a web server by using the http as the protocol. Since the browser now knows that the protocol is HTTP, it knows how to interpret everything located to the right of the forward slashes. It also knows that it is talking to universalteacherpublications.com and is asking for the file ebooks.htm. Since we did not define a port to use, the browser assumes that port 80 is the default port used to exchange data with the web server.