The Certideal warranty is very similar to the manufacturer's warranty.
All issues unrelated to your usage are covered. Here's a list of the issues covered:
Network
Wi-Fi / Bluetooth
GPS
Speaker, internal earphones, microphone
Camera (front and rear) / Flash
Touchscreen
Charging port
Face ID
Touch ID / Home button
Phone doesn't turn on
Vibrator
Battery
In summary, if you accidentally drop your phone in water or from a third-floor window, it is not covered by the warranty. However, if the issue is not directly related to your usage, it is covered.