AWS CDK (Cloud Development Kit) is an open-source software development framework that allows developers to define cloud infrastructure in code. One of the key features of the AWS CDK is the ability to use CDK Synth to generate CloudFormation templates from the code.

CDK Synth is a command-line tool that takes the code written in the CDK and converts it into a CloudFormation template. This allows developers to easily manage their cloud infrastructure as code, making it easier to version control, test, and automate deployments.

To use CDK Synth, you first need to have the AWS CDK installed on your machine. Once you have the CDK installed, you can use the "cdk synth" command to generate a CloudFormation template from your CDK code.

For example, let's say you have a CDK code that creates an S3 bucket. The code would look something like this:

import * as cdk from 'aws-cdk-lib';
import * as s3 from 'aws-cdk-lib/aws-s3';

export class MyStack extends cdk.Stack {
    constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
        super(scope, id, props);

        new s3.Bucket(this, 'my-bucket');
    }
}

To generate the CloudFormation template for this code, you would run the following command:

cdk synth

This would generate a CloudFormation template that creates an S3 bucket. The template would look something like this:

{
    "Resources": {
        "my-bucket": {
            "Type": "AWS::S3::Bucket"
        }
    }
}

This is a simple example of what CDK Synth can do, but it can be used for much more complex infrastructure as well. For example, you can use CDK Synth to generate a CloudFormation template for a multi-tier application that includes an S3 bucket, an Elastic Beanstalk environment, and an RDS database.

In conclusion, CDK Synth is a powerful tool that allows developers to manage their cloud infrastructure as code. By using CDK Synth, developers can easily version control, test, and automate deployments of their cloud infrastructure. With the use of CDK Synth, developers can easily create and manage their cloud resources.