Azure Functions is a solution for easily running small pieces of code, or “functions,” in the cloud. You can write just the code you need for the problem at hand, without worrying about a whole application or the infrastructure to run it. Functions can make development even more productive, and you can use your development language of choice, such as C#, F#, Node.js, Python or PHP. Pay only for the time your code runs and trust Azure to scale as needed. Azure Functions lets you develop serverless applications on Microsoft Azure.

 
Azure Functions consumption plan is billed based on resource consumption and executions. Pricing can be found here

What can I do with Functions?

Azure Functions is a great solution for processing data, integrating systems, working with the internet-of-things (IoT), and building simple APIs and microservices. Consider Functions for tasks like image or order processing, file maintenance, or for any tasks that you want to run on a schedule.
Functions provides templates to get you started with key scenarios, including the following:

  • BlobTrigger – Process Azure Storage blobs when they are added to containers. You might use this function for image resizing.
  • EventHubTrigger – Respond to events delivered to an Azure Event Hub. Particularly useful in application instrumentation, user experience or workflow processing, and Internet of Things (IoT) scenarios.
  • Generic webhook – Process webhook HTTP requests from any service that supports webhooks.
  • GitHub webhook – Respond to events that occur in your GitHub repositories. For an example, see Create a webhook or API function.
  • HTTPTrigger – Trigger the execution of your code by using an HTTP request.
  • QueueTrigger – Respond to messages as they arrive in an Azure Storage queue. For an example, see Create an Azure Function that binds to an Azure service.
  • ServiceBusQueueTrigger – Connect your code to other Azure services or on-premises services by listening to message queues.
  • ServiceBusTopicTrigger – Connect your code to other Azure services or on-premises services by subscribing to topics.
  • TimerTrigger – Execute cleanup or other batch tasks on a predefined schedule. For an example, see Create an event processing function.

Azure Functions supports triggers, which are ways to start execution of your code, and bindings, which are ways to simplify coding for input and output data. For a detailed description of the triggers and bindings that Azure Functions provides, see Azure Functions triggers and bindings developer reference.

Find our more here 

Azure Functions on Web Hack Wednesdays