Final answer:
A digital certificate is used to secure connections between clients and servers, typically involving a web server for websites using HTTPS.
Step-by-step explanation:
The device protected by a digital certificate is typically not a physical device but rather refers to a server or a service that employs the certificate for securing communications. Digital certificates are used to authenticate the identity of the server or service and to enable encrypted connections between clients (like web browsers) and servers (such as a website using HTTPS).
For example, when you visit a secure website, the web server presents a digital certificate to your browser to establish a secure connection using the Transport Layer Security (TLS) protocol.