According to Wikipedia, "Serverless computing is a cloud-computing execution model in which the cloud provider runs the server, and dynamically manages the allocation of machine resources". The aime of Serverless is to remove the overhead of managing and scaling of the underlying infrastructure, allowing focus to shift to the application and business value.
Within the concept of Serverless is a category of Functions as a Service (FaaS). FaaS enables the creation of focused building blocks that can be executed without the the complexity of building and maintaining the infrastructure. These functions can solve very targeted problems in various languages to give you flexibility and increased velocity.