Questions related to Suspend Mode, which is a special low-power mode often used on laptops that preserves the contents of RAM while using less power than normal. Questions related to suspending to disk should use the [hibernate] tag.
Suspend (to RAM) is a power saving mode. The machine state is held in RAM with the minimum of power needed to preserve all data. When the user wants to continue the session, they should be able to resume from suspend instantly.
Many laptops activate suspend mode automatically when the lid is closed while running on battery, or can be configured to do so. Suspend can also be activated through a GUI button or on the command line - for example, in versions of Ubuntu that use systemd, such as 16.04, suspend can be activated using the systemctl interface
A related tag is acpi which refers to the open standard for power management interfaces. Suspend as defined by ACPI is "S3"
