Google play store is a huge library of apps.Its a Goolge Android app which only support on android OS.One can easily access with a gmail account.
It is time saving before to download a particular app we have to go to the different site such etc, but with play store u can find all your favourite app is one place at the same time.
The low part is security level is very low n it is full of malware and some apps are fake apps to fool the people so to access the play store one should read about it.