What is the advantage of using REST instead of non-REST HTTP?

Simply put, REST means using HTTP the way it's meant to be.

Have a look at Roy Fielding's dissertation about REST. I think that every person that is doing web development should read it.

As a note, Roy Fielding is one of the key drivers behind the HTTP protocol, as well.

To name some of the advandages:

• Simple.
• You can make good use of HTTP cache and proxy server to help you handle high load.
• It helps you organize even a very complex application into simple resources.
• It makes it easy for new clients to use your application, even if you haven't designed it specifically for them (probably, because they weren't around when you created your app).

IMHO the biggest advantage that REST enables is that of reducing client/server coupling. It is much easier to evolve a REST interface over time without breaking existing clients.

I recommend taking a look at Ryan Tomayko's How I Explained REST to My Wife

Third party edit

Excerpt from the waybackmaschine link:

How about an example. You’re a teacher and want to manage students:

• what classes they’re in,
• what grades they’re getting,
• emergency contacts,
• information about the books you teach out of, etc.

If the systems are web-based, then there’s probably a URL for each of the nouns involved here: student, teacher, class, book, room, etc. ... If there were a machine readable representation for each URL, then it would be trivial to latch new tools onto the system because all of that information would be consumable in a standard way. ... you could build a country-wide system that was able to talk to each of the individual school systems to collect testing scores.

Each of the systems would get information from each other using a simple HTTP GET. If one system needs to add something to another system, it would use an HTTP POST. If a system wants to update something in another system, it uses an HTTP PUT. The only thing left to figure out is what the data should look like.

Caching.

There are other more in depth benefits of REST which revolve around evolve-ability via loose coupling and hypertext, but caching mechanisms are the main reason you should care about RESTful HTTP.

• Give every “resource” an ID
• Link things together
• Use standard methods
• Resources with multiple representations
• Communicate statelessly

It is possible to do everything just with POST and GET? Yes, is it the best approach? No, why? because we have standards methods. If you think again, it would be possible to do everything using just GET.. so why should we even bother do use POST? Because of the standards!

For example, today thinking about a MVC model, you can limit your application to respond just to specific kinds of verbs like POST, GET, PUT and DELETE. Even if under the hood everything is emulated to POST and GET, don't make sense to have different verbs for different actions?

Query-strings can be ignored by search engines.