But after all what is a SaaS?

The two fundamental characteristics that differentiate a " Software as a Service " or on demand, from a normal software, also called on premisse , are:

• It is centralized somewhere, usually a public cloud, but not necessarily.
• Payment is made according to usage, or a periodic value or per unit of consumption, such as time, operations, moving numbers (employee numbers, certificates issued, etc.), or any other formula that makes sense .

In general, you "buy" more than the software, buy the infrastructure, and have complete support for what you need. No need to worry about the hardware, network, backup, maintenance, structure, update, etc.

This is not always true. There are cases where only the monthly payment model or something like that already characterizes a SaaS. But there are those who disagree with these cases.

In thesis is a "pay to use". Pay according to demand and this would make the costs lower. In practice it is common for costs to be greater.

It is common in web software, but nothing prevents it from using other forms. It is common to need a client, mobile or desktop to access the core software.

There are often gains for sharing resources (even people) among all users. But there is a cost in trying to make everything work well for everyone in the same environment. It can be even more complicated or cost a lack of flexibility offered.

Some people complain about lack of control, safety and convenience. It is not easy to identify how good a solution is.

It also sells itself to the idea that it is more predictable thus. In practice whenever the supplier has additional costs, not foreseen, it ends up passing on to the customer. What may happen is to have fewer unforeseen costs from the supplier experience, but this is not guaranteed. Depending on the model adopted the cost may be much less predictable. And when it is predictable, it ends up charging for the maximum it would spend, for the worst case, which is no advantage whatsoever.

This is a way to improve the revenue of the industry, so much so that after that, it exploded the billing of many companies in the industry, from cloud vendors, as well as products that were previously sold without this model, including basic and specific software. If the industry is charging so much more then they did not offer less costs as promised. This occurred just when the current (now old) billing model was showing saturation. Some people will say that they are selling more software than before. I saw no evidence of this.

It is a way for the industry to combat piracy.

Finally, it has advantages, but it also brings disadvantages and I will not list all because it is not even the focus of the question.

He has siblings: IaaS , PaaS , DaaS , MBaaS , among others.

Using Azure as an example,

TheaboveimageattemptstoillustratethedifferencebetweeneachoftheavailablecloudmodesinAzure.

• IaaS-InfrastructureasaService:Theproviderprovidestheentireinfrastructureforuserconfiguration.Thishasaccesstovirtualmachinesandserverstobeconfigured,allowingacontrolovertheavailableenvironment.Forthepublicationofawebsite,forexample,theusermustconfiguretheapplicationserver,theaccessports,thefirewall,etc.
• PaaS-PlatformasaService:Theproviderprovidesatemplatewheretheinfrastructureisabstracted,andtheuserhastoworryonlywiththeplatformconfiguration.Thismodelhascertainlimitations,butitmakesitsconfigurationmucheasierandmoreagiletoperformbecausetheuserdoesnothavetoworryabouttheinfrastructureneededtoruntheapplication.Topublishawebsite,forexample,itisonlynecessarythatyoucreateaPaaSwiththenecessarysettingstorunyourwebsite,andpublishitthroughFTP,forexample.
• SaaS-SoftwareasaService:Theproviderprovidesbothhardware(Infrastructure)andsoftware(Platform)asaservice.Theuserdirectlyaccessesthesoftwarehere,withouttheneedtomaketechnicalsettingsforthis.HereareexamplesofOffice365,calendarsande-mailservices.

  

Andwhatarethemaindifferencesforso-callednormalsoftware?

WhenwetalkaboutSaaSandwetalkaboutcloud,itisimportantthatthesoftwareobeysthecharacteristicsthatdefineacloudtechnology.Thisisthemaindifferencebetweenasoftwareasaserviceandasoftwaresaidnormal.

Forinformation,seebelow characteristics considered essential for a technology to be considered cloud .

• On-demand self-service: The user must be able to provision resources for the cloud without the need for human interaction to do so.
• Broad network access: Basically, the provider must make the service available so that it can be accessed through the internet.
• Rapid elasticity: The provider should make it possible for the consumer to rapidly increase or decrease their resources in certain scenarios. You can think of elasticity as a feature so the user does not spend resources unnecessarily, thereby paying more for it. A shopping website can use the quick-elasticity service during a promotion, such as black friday, for example.
• Measured Services: The provider should provide a way to measure the resources used by the service so that it can monitor and control it, thus building better transparency between the consumer and the provider.