Azure functions is a logical unit of code that lets you execute your code in a server less environment without worrying about application infrastructure. It provides updated infrastructure and your application runs at a scale automatically whenever there is a load.
You can develop your function code using C#, Java, JavaScript, Powershell, and Python languages of your choice. Package managers like Nuget and NPM are supported so you can use popular libraries in your application logic.
Azure functions are surrounded by triggers and bindings. A function is triggered by a specific type of event.
Once the functions are developed and deployed to azure, then you can pay per use pricing model. The plans will be App Service Plan, Consumption Plan, and Premium plans.