I was interested in what webhooks are, but there was no link in the article. Aha! I thought to myself, I'll look it up on the internet, and behold there was webhooks.org, which I assume is its home. Going there I find no description of what it is, a broken link to the blog, and a wiki that does not exist. So I guess it's not ready for primetime?
Webhooks are very common for server-to-server communication and have been in use for several years (though they only really took off in the last couple). They are ready for primetime and there are lots of best-practices in the industry around how to implement and use webhooks.
They also go by other names such as: PubSubHubBub (PSHB), real-time API, push API, web callbacks... Basically it is just a URL endpoint that accepts POST requests with form data or JSON body payloads that come from server-generated events from other systems.
Some geek-focused services allow you to configure a webhook that will be triggered in response to [domain specific stimuli], such as a new order placed on your Shopify store.
The webhook is just the URL of a service that responds to the request in a hopefully useful way. When someone purchases my item, Shopify will post a request to the URL that contains useful information about the action.
In this manner, I can build interesting services that respond to events that happen on other websites. Providing webhooks is a pretty awesome thing to do, but it's not useful for non-developers in 2012.
It's a way to link, or "hook" to a web based service. You provide a URL where you want to receive event information, and when an event happens the server will HTTP POST the relevant information to the URL. This way, you don't have to constantly poll the service asking "did an event happen yet?"; the server will notify you automatically.
