When it comes to the end of your computing day, you have a number of options. You could leave the computer on and walk away. That's not really viable as it continues to take power and will significantly shorten the life of your components.
You could put it into sleep mode. Sleep is considerably faster to come back from than a full shutdown and needs less power, but not no power. Sleep effectively writes the state of your computer at that moment to its memory and then shuts everything else down. It must still be powered though, whether by mains or battery, so that the memory can retain the information. If you're only stepping away relatively briefly, but long enough to warrant a state-change, then sleep is probably the way to go. Interestingly, Macs go to sleep, rather than full shutdown, by default.
Hibernate is another option (in some systems). As its description suggests it is like sleep, only more so. Hibernate saves the computer's state, but this time to the hard drive rather than the memory. That means it takes essentially no power to maintain but does take a significantly longer time to boot back up. If you feel you can live without hibernate in Windows, then switch it off as it reserves a chunk of hard drive space that you can claim back if you don't use it. Microsoft tells you how.
Then, of course, there's shutdown. This closes all the windows, locks all the doors, gives the place a quick vacuum and leaves a note for the milkman. Windows especially needs a shutdown occasionally. If any programs have been updated, particularly Windows itself, there may be specific files that cannot be updated until they are no longer used, and that's only going to happen after a shutdown.
So at the end of your computing day choose your method and both head to the land of sleep. Or indeed hibernation.