Can a Trojan virus spy on you?

Could it be possible for a Trojan virus to secretly observe and gather information about you without your knowledge? Are there specific methods or techniques that a Trojan virus might use to spy on your activities, including your online browsing habits, personal data, or even your private conversations? Is it important to be aware of the potential risks associated with Trojan viruses and to take steps to protect yourself from their potentially harmful effects?