Ngrok is a powerful tool that helps developers expose local servers behind NATs and firewalls to the public internet over secure tunnels. It simplifies the process of debugging and demonstrating web applications directly from a local machine, making it easier to collaborate on development projects and test applications on mobile devices without deployment. The service at https://ngrok.com offers features like instant secure URLs to your localhost server, detailed traffic inspection and replay, and integration capabilities for secure tunneling in different environments. It's widely used for use cases that range from quick demos to extensive testing, and is trusted by developers for its ease of use and robust performance.