A browser is a program that lets you see and hear all the information that's on the World Wide Web. There are several types of web browsers out on the market. The most popular one is Netscape Navigator, which is used by about 70% of the people online.
Using a World Wide Web browser, a bookmark is a saved link to a Web site (Netscape uses the bookmark idea; Internet Explorer calls them "favorites."). When you are looking at a particular Web site or home page and want to be able to get back to it at a later time, you can create a bookmark for it.
You can think of your browser as a book that's full of millions of pages -- Web pages. The bookmarks act as favorite spots that you'd like to go back and look at again.