What is SpeechSynthesisServer on macOS?

/System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/SpeechSynthesis.framework/Versions/A/SpeechSynthesisServer.app/Contents/MacOS/SpeechSynthesisServer

Implements speaking hotkey and time announcements text-to-speech features

SpeechSynthesisServer is a user-level daemon that runs only when the user has enabled the speaking hotkey feature (Accessibility preference pane) or time announcements features (Date & Time preference pane). The daemon will continue running while either feature is enabled.

The binary is a part of SpeechSynthesisServer application.

source: man