According to the O’Reilly HTML Reference, “the DIV element gives structure and context to any block-level content in the document. Each DIV element becomes a generic block-level container for all content within the required start and end tags.”
So the DIV tag is a powerful generic element well suited for being used as a container within our Web page rahter than tables or cells because the div tag can be use for creating sections or (div)isions of Web pages.
The concept is very intuitive. Instead of using tables as layout elements, we can use DIVS as excellent content containers to build our page layout. In conjunction with several CSS declarations, DIVS based layout are pretty easy to get.
They reduce the amount of code in our documents which is good for the search engine and if we use an external style sheet we will be separating the formatting/presentation information from the content which is great for maintenance and readability.