What if you close the lid of your laptop without shutting it down ?

If you are using other than any mac device and you close the lid of your laptop then the background processes you left while using will be running in background upto the time limit for your device to go into sleep mode.Before going to sleep mode
every running process will be going (e.g. virus scanning , running downloads etc ) . It also saves your device state as you left it like you were working on an excel or word file , that file state will be saved .so there

pros 

1. your machine state will be saved and you will be able to find exactly what you left off
2. you can go out without saving the file by just putting the lid down
3. your background processes will run , so you don't have to sit the entire time infront of your screen(NB- upto sleep mode )

cons

1. It will consume your battery a lot

unlike the fact that mac users don't have this problem