AWS Lambda is a "serverless" service provided by Amazon Web Services (AWS) that allows developers to execute code without managing or provisioning servers. With Lambda, developers can write functions and upload them to run in the cloud on an as-needed basis without managing infrastructure.
It operates based on "event triggers" that initiate the code, such as uploading a file to an Amazon S3 bucket or receiving a message in an Amazon Simple Queue Service (SQS) queue. Lambda scales automatically to meet the code's demands, and developers only pay for the actual compute power used, as billing is based on the number of function invocations and their duration.