It is true that you need an ISP, however, if it is AOL and you have a broadband connection and use a router, you don't have to use the AOL browser, unless you need the extra content you don't get with IE.
Internet explorer is a browser, like firefox and opera which are alternatives.
Without a browser you would connect to the internet through the ISP but be unable to surf it. The browser locates and displays web pages, using search engines such as google and yahoo.