Azure offers a set of PAAS(Platform-As-A-Service) offerings known as App Services. Web Apps and Web Jobs are two of the services under the App Services category.
Before Azure Web Apps, in order to deploy web applications built using the .Net framework, we needed an infrastructure comprising of software and hardware. For example - we needed a machine with a windows operating system, along with the .Net framework components and an IIS web server. We could scale up, but if we needed to scale out, we had to replicate this process several times.
With Web Apps we can now deploy a web application to a Web App without having to worry about setting up any of the underlying infrastructure. Our web application can be up and running in just a few minutes. We can also scale up (i.e. increase the processing power) or scale out (increase the number of instances) very easily via the Azure portal. We can also use Web App as a pre-production environment as well in order to test our application before we go live. We can also do a/b testing with one Web App instance running the production code and another Web App instance running the new features that we are testing. We can then very easily swap the existing production instance with the pre-production instance if needed.
Azure Web jobs are used for deploying batch jobs without worrying about the underlying infrastructure. An example of a batch job that can be deployed to a Web Job would be a windows service. In the past, if we developed a windows service, we needed an infrastructure similar to the web application, in order to install it and run it. With Web Jobs, we just deploy our windows service .exe file to a Web Job and everything is ready to go. Windows Services usually work in tandem with web applications so a Web Job is deployed to the same instance as the related Web App. It is also very easy to debug the Web Apps and Web Jobs.
NOTE: Web Apps and Web jobs support other platforms and languages like Java and Python and others in addition to the .Net platform.
