At the heart of the container is your code, which, as a rule of thumb, has to be written specifically to perform a single task or a few simple processes; similar to how you would write functions in your normal code. Each Lambda project that you deploy can thus be termed as a Lambda function, or just a function. At the time of writing this book, AWS supports Java, Python, Node.js, and even C# as programming languages for your functions. Each function can be invoked either on demand or invoked dynamically based on certain types of supported events. A few event examples are listed out as follows:

Amazon S3: Lambda functions can be triggered when an object is created, updated, or deleted in an S3 bucket

Amazon DynamoDB: Lambda functions are triggered when any updates are made to a particular DynamoDB table, such as row insertion, deletion, and so on

Amazon Simple Notification Service (SNS): Trigger a Lambda function when a message is published on a, SNS topic

Amazon CloudWatch Logs: Use Lambda functions to process CloudWatch Logs as feeds

Scheduled events: Run Lambda functions as scheduled events, just like a cron job

AWS CodeCommit: Execute Lambda functions whenever new code is pushed to an existing branch, and so on