The GWTPHP Framework here says the following:
One of the advantages of Web 2.0 based applications is that the traffic between client and server consists only of data. You don’t need to send long HTML code that defines design, only data - so the communication and reloads are very fast.
I don't seem to understand this, if HTML data is not sent to the browser, how does the Browser format and display the data?
Javascrpt + css most likely.
Web 2.0 is a dead buzzword as of now, fortunately.
-Edit- To clear things out since there is a confusion. Web 2.0 as a term is dead since it never meant anythin useful. There are some random concepts typically associated with Web 2.0 which are not dead but noone really uses Web 2.0 term anymore - just compare it to 2 years ago and you WILL see the difference.
Looks like the next line in the link you mentioned clarifies it to some extent.
data exchange between browser and server using JSON encoded requests.
Client side js further parses this JSON Object and convert it to appropriate visual content.
It mentions about JSON.
JSON (JavaScript Object Notation) is a lightweight data-interchange format.JSON is built on two structures:
* A collection of name/value pairs. In various languages, this is realized as
an object, record, struct, dictionary, hash table, keyed list, or associative
array.
* An ordered list of values. In most languages, this is realized as an array,
vector, list, or sequence.
Read this article
Advantages and Disadvantages of Web 2.0
For a list of web2.0 applications
Basically the idea is that the raw data is moved between the client and server, then the client renders the data.
For example, consider a table of data.
With HTML you would send the TABLE, TH, TR, TD elements, plus any style information, all along with the actual data.
With Web 2.0 and Ajax, then a script can pull the data down, and then add its own TABLE, TH, etc. elements.
Also, you can easily update a fragment of the page rather than the entire page, which also saves traffic.
The statement is not completely true. Of course, some kind of formatting information is transferred. The point is that it is not continually transferred.
Typically, the whole page is downloaded (HTML + data) to start with and from that point on only data is transferred. For example, a country is selected from one pulldown and this triggers a lookup of main cities for that country. Only the city names will be transferred and not the whole page. The city names may then be inserted into a second pulldown list using javascript .
Web 2.0 reduces bandwidth usage as you mentioned.
You said only data is transferred from client to server not complete HTML page, it is quite true but not completely. First time whole page with complete HTML, CSS and JS is sent from server to client when requested and after that in subsequent requests(Dynamic) only data is transferred in between client and server which can be in JSON or XML or any other format.
So client have HTML structure and just need data to show it on browser like in case of tables or some forms.
That quote (and many of the answers) are right on about the advantages of using AJAX (or similar technologies) to reduce data transfer requirements and improve the responsiveness of a web site.
Whether that's an advantage of "Web 2.0" is arguable because "Web 2.0" has no commonly-agreed or widespread definition. It certainly does not have any application or protocol specification, like, say, XML 1.0 or HTML 4.01.
If "Web 2.0" means "uses AJAX", then, yes, it is an advantage of "Web 2.0" - but I know of many sites which use AJAX and have never presented themselves as being "Web 2.0". There are also a few out there which call themselves "Web 2.0", but only use full-page loads and no AJAX.
If "Web 2.0" means "social networking", "has a brushed-metal look and rounded corners", "uses bright colors, simple shapes, and a reflection effect on the logo", or any of the many other definitions of "Web 2.0" that people have been seen to operate under, then AJAX and its benefits have nothing to do with it.
"Web 2.0" is a marketing buzzword which, like any good buzzword, means something different to each person who uses it. It is not an actual technology.
The question in your title is different to the one in the body (which has been answered well enough already).
As for the title, you have to remember that 2.0 doesn't just mean the mechanics of AJAX and JSON and image spriting or whatever. For the end user it really means page interaction without reloads, it means snappier UI and it means slick UI features like hot loading image sliders (and any number of things which have been very possible since web 1.0).
It means user-driven content whether that's flickr, blogs, or posting comments on blogs, and it means search driven increasingly be recommendation and reputation rather than pure organic look-ups (more digg, less google).
2.0 is about changing the way the end-user works with the browser, how that's achieved on the back-end is really secondary (as always).
The whole back-button conundrum-- was it any better with old-school cgi apps? Those are horrible in comparison. Web 2.0 is another catchphrase for interactive websites using newer and more powerful technologies such as rich javascript and powerful serverside frameworks and languages. web 1.0 also is a catchphrase, but it is a derogatory one coined with web 2.0 that means, this site is old and needs some work. To a certain extent it doesn't matter... take a look at http://www.web20generator.com/. It's more of an umbrella phrase that people use to describe things. For all that it matters, we could be at web five-million point three.