The orange dot on an iPhone indicates that an app is using the microphone. This feature was introduced with iOS 14 as a security measure to inform users when their microphone is being accessed by an app. It does not necessarily mean that someone is listening in, but it's a visual indicator that the microphone is in use. You can check which app is using the microphone by swiping down from the upper right corner to access the Control Center. If you are concerned, you can deny microphone access to specific apps by going to Settings, Privacy, and Security, and selecting Microphone