What it means
Theft Detection Lock uses device motion and other signals to identify a likely snatch of an unlocked phone and automatically locks the screen. Remote Lock is a deliberate request by the owner through android.com/lock using a verified phone number and, if configured, a security question. The automatic feature may miss a theft; the remote one depends on prerequisites and network delivery. Neither replaces Find Hub's fuller locate or erase workflow.
A real-world example
A thief quietly takes a phone from a table. There may be no running-away motion for Theft Detection Lock to recognize. The owner notices later and uses Remote Lock from a friend's device, but the request waits until the phone comes online.
What to do
Enable both where supported, keep a strong screen lock and prepare the verified number before a loss. In an incident, act through Find Hub and the carrier as well; do not wait for the automatic sensor.
The distinction that matters
The automatic motion feature only operates on an unlocked screen, while an owner-requested remote lock waits for connectivity. A lock prevents some later access but does not undo information already viewed or sessions already stolen. If the thief knows the PIN, change related account credentials and recovery settings from another trusted device, not merely the missing handset's lock status.
Google Android theft controls