Which component corresponds to the Suspend feature?

You might want to read the S0ix thread:

Generally failing to suspend usually is a symptom from S0ix sleep being enabled but the kernel not properly powering down all components.

You can sometimes (it depends on the device BIOS) revert back to S3 sleep.
Read the “Improve the S0ix experience under Linux” thread for more info, but you can try adding mem_sleep_default=deep to your kernel parameters.