Saas is software as a service. This is where you host applications through the subscription model. You pay as you go. Paas is platform as a service. You build and execute custom applications, exposing them as services. Finally Iaas is infrastructure as a service. This is like the normal hosting you know and love.
Azure attempts to deliver the benefits of Paas, which remaining as flexible as Iaas. It provides a hosted application server. Azure needs a lost of hardware to run. Data centers are staffed by a few good men who take advantage of automating everything. In other words, you don’t have a man in the loop.
Azure has a policy based deployment strategy. The pricing is mostly simple to understand. The exceptions are the pricing for blobs and tables. Maybe I will detail those more complicated pricing policies later.