You might have seen two options known as Sleep and Hibernate in your computer that is loaded with Windows Vista or Windows 7 for temporarily suspending the operations of the computer. Apparently, these two options are entirely different from Shutdown option which would permanently halt the system.
Both of these commands will be useful if you intend to leave for time being and wanted to start from the point where did you left when you come back.
Interestingly, there are significant differences between Hibernate and Sleep in consumption of power, time taken to restart, Usage system resources etc. Based on the need you have to choose between these two options when you want to suspend the operations of the computer temporarily.
Sleep is a power-saving state that allows a computer to quickly resume full-power operation (typically within several seconds) when you want to start working again. Putting your computer into the sleep state is like pausing a DVD player: The computer immediately stops what it’s doing and is ready to start again when you want to resume working.
Although power consumption during sleep state is lower than it is during full working state, the computer is still alert enough to be able to resume working again – almost immediately – when the user is ready. Basically, standard sleep state stores your current system status (open files, settings, etc.) in RAM, so your PC continues to draw enough power to keep that memory active. Since nonessential components are shut down, some energy is saved, but the "awake" RAM allows the PC to come to life much faster than it would if it were turned off or in hibernation mode.
When a computer goes into hibernation, it basically takes a snapshot of your current system status, including current settings as well as open applications and files. It then, in turn, writes this information to the hard disk and shuts down the computer. When you're ready to resume work, the computer accesses this stored information, returning the PC to the same point it was before hibernation kicked in. Although a computer generally comes out of hibernation faster than it performs a full reboot, the process does take longer than it would to come out of standard sleep state. It's more common to use hibernation mode with a laptop than a desktop due to battery considerations.
Hibernation is a power-saving state designed primarily for laptops. While sleep puts your work and settings in memory and draws a small amount of power, hibernation puts your open documents and programs on your hard disk, and then turns off your computer. Of all the power-saving states in Windows, hibernation uses the least amount of power. On a laptop, use hibernation when you know that you won't use your laptop for an extended period and won't have an opportunity to charge the battery during that time.
Hybrid sleep is designed primarily for desktop computers. Hybrid sleep is a combination of sleep and hibernate—it puts any open documents and programs in memory and on your hard disk, and then puts your computer into a low-power state so that you can quickly resume your work. That way, if a power failure occurs, Windows can restore your work from your hard disk. When hybrid sleep is turned on, putting your computer into sleep automatically puts your computer into hybrid sleep. Hybrid sleep is typically turned on by default on desktop computers.
As its name suggests, hybrid sleep is a mode that lies somewhere in the middle between sleep and hibernation. In this state, Windows records system information about open applications and files both in RAM and on the hard disk. In this sense, hybrid sleep is like standard sleep state with a failsafe provision in case there is a power outage or the machine shuts down while in sleep state.
That is, since the computer's information is stored in RAM, the PC will resume much quicker than if it were in hibernation or full shutdown mode – just like with standard sleep. The problem is, in the event of a power outage, this information would be lost so any unsaved work may be unrecoverable. However, since Windows also stores this information to the hard disk before going into hybrid sleep state, there is a backup of the work that can be restored in case of power failure. This power-saving state is more commonly used in desktop computers.