Answer may be:

AWS Lambda (or lambda in short) is an event-driven, serverless compute service offered by Amazon Web Services (AWS) that compute the code in response to the event and also manages the resources automatically So that one does not need to look after the resources required to execute the code.

It allows users to simply focus on computational logic and desired outcome instead of worrying about resources such as operating systems, scaling, etc. Once the code is provided, it runs the code on high availability infrastructure, manages all the resources, and performs all the essential activities including server, operating system maintenance, security patch deployment, etc. AWS Lambda can also be used to extend the functionality of other AWS services using custom logic.

Here the terms used for AWS Lambda:

Serverless:

When we say lambda is a serverless compute service, It does not mean that server is not used or involved. Here serverless means the developer does not need to maintain the server on its own. Lambda is a fully managed service that looks after resources and infrastructure by itself.

Event-driven:

Here event driven means to drive this service an event must take place. The developer will mention the event and when that event will take place, it will then trigger the lambda function to perform the computation or execution of the code.

For more details, read the full blog:

What is AWS Lambda?