Amazon Nova is a foundation model created by Amazon and is offered as one of the models you can use in AWS Bedrock, so the model gets a marketing page for it. Note that Llama also has an AWS marketing page (as do other models), but that doesn’t make them AWS products: https://aws.amazon.com/bedrock/llama/
Amazon Nova Chat is a different product that uses Nova, buts it not AWS. Notice that if you try to use Nova Chat, you log in using your Amazon.com account and not an AWS account.
AWS already has Amazon Q, which is its chatbot offering for AWS customers.