Here, myHandler is the name of your handler function. By exporting it, we make sure that Lambda knows which function it has to invoke first. The other parameters that are passed with the handler function are:

event: Lambda uses this parameter to pass any event related data back to the handler.

context: Lambda again uses this parameter to provide the handler with the function's runtime information such as the name of the function, the time it took to execute, and so on.

callback: This parameter is used to return any data back to its caller. The callback parameter is the only optional parameter that gets passed when writing handlers. If not specified, AWS Lambda will call it implicitly and return the value as null. The callback parameter also supports two optional parameters in the form of error and result; error will return any of the function's error information back to the caller, while result will return any result of your function's successful execution.