Most websites create the webpage on the server. Once your browser receives it, it parses and displays it once. Compare it to a salad - most restaurants prepare

Most websites create the webpage on the server. Once your browser receives it, it parses and displays it once. Compare it to a salad - most restaurants prepare their salads in the kitchen. The waiter takes one trip to deliver your plate, and all you have to do is eat. What Twitter was experimenting with was a thick client. The initial page load would contain little more than the basic Twitter architecture and a URL, and this architecture would send off more requests (individual tweet, profiles, responses, lists) based on the contents of the URL, updating the page to fit what it gets back each time. In a salad bar, you don't get one plate. There's a whole barrage of vegetation to select from, and you have to walk around yourself to get any of it. You also have to spend time deciding what you want. Metaphorically, the salad-eater is your web browser, and that time it takes to send and receive more requests, as well as make decisions and display the results, turns a 140-character message into a slowly loading behemoth.