AWS Lambda is a compute service within the AWS ecosystem. It lets you run code in response to events (HTTP, Timers, other AWS Services).
AWS Lambda manages the underlying infrastructure of your application, including automatic scaling, as well as the security the underlying operating system and all hardware, allowing you to focus your development time on writing code.
With Lambda, you can run code for virtually any type of application or backend service with zero administration. Just upload your code and Lambda takes care of everything required to run and scale your code with high availability. You can set up your code to automatically trigger from other AWS services or call it directly from any web or mobile app.