A web browser is a computer program which downloads and displays web pages on the World Wide Web (or a local device). The original internet browser was NCSA Mosaic. Before long, however, Netscape and AOL became most popular, while NCSA Mosaic became obsolete.
There are five major web browsers currently in use; Internet Explorer (replaced by Edge), Firefox, Safari, Opera, and the Chromium-based Google Chrome. Google Chrome currently holds the largest "market share" in desktop browsing.
Other browsers are carving niches such as Dolphin for Android phones, Pale Moon for Atom processors, and Firefox for the privacy-conscious.