__Serverless computing__ is a cloud computing execution model in which the cloud provider allocates machine resources on demand, taking care of the Server (computing) on behalf of their customers - wikipedia
Serverless computing does not hold resources in volatile memory; computing is rather done in short bursts with the results persisted to storage. When an app is not in use, there are no computing resources allocated to the app. Pricing is based on the actual amount of resources consumed by an application.
It can be a form of utility computing. "Serverless" is a misnomer in the sense that servers are still used by cloud service providers to execute code for developers. However, developers of serverless applications are not concerned with capacity planning, configuration, management, maintenance, fault tolerance, or scaling of containers, Virtual machine, or physical servers.
Serverless computing can simplify the process of software deployment into production. Serverless code can be used in conjunction with code deployed in traditional styles, such as microservices or Monolithic application. Alternatively, applications can be written to be purely serverless and use no provisioned servers at all. This should not be confused with computing or networking models that do not require an actual server to function, such as peer-to-peer (P2P).