Service และประเภทของมันใน Android คืออะไร?

A SERVICE runs operations WITHOUT a UI (not tied to a screen):
  → for work that should continue regardless of UI (or independent of any activity)
  → declared in the manifest; runs in the app's process (main thread by default — must
    move heavy work off it!)

FOREGROUND SERVICE → user-aware, ongoing work with a PERSISTENT NOTIFICATION:
  → music playback, navigation, active location tracking, ongoing downloads
  → higher priority (less likely to be killed); the notification is required
BACKGROUND SERVICE → work without user awareness:
  → heavily RESTRICTED on modern Android (battery) → often use WorkManager instead
BOUND SERVICE → other components BIND to it for a client-server interface (interact with
  it, call methods); lives while bound