The Azure WebJobs SDK is a framework that simplifies the task of writing background processing code that runs in Azure WebJobs. It includes a declarative binding and trigger system that works with Azure Storage Blobs, Queues and Tables as well as Service Bus. The binding system makes it incredibly easy to write code that reads or writes Azure Storage objects. The trigger system automatically invokes a function in your code whenever any new data is received in a queue or blob. The SDK also provides an integrated Dashboard experience in the Azure management portal, with rich monitoring and diagnostics information for your WebJob runs.
The related repo azure-webjobs-sdk-extensions demonstrates the extensibility model of the SDK and contains many useful trigger/binder extensions (e.g. WebHooks, SendGrid, Timer/Cron, Files), as well as samples showing how to use/create SDK extensions.