Named Credentials and Two way SSL are two security methods that an integration architect can leverage within Salesforce to secure the integration with an external system via HTTPS request. Named Credentials are a type of metadata that store authentication settings for accessing external services. They allow you to specify the URL of a service,the authentication protocol, and the credentials for accessing the service. Two way SSL is a type ofmutual authentication that requires both the client and the server to present their certificates to each other. This ensures that both parties are who theyclaim to be, and that the communication is encrypted. Two way SSL can be configured in Salesforce by uploading a certificate and a private key, and associating them with a named credential. References: Certification - Integration Architect - Trailhead, [Named Credentials],
[Mutual Authentication]