Google Play Services is a core Androids app that keeps your other apps up-to-date. Google Play is more than an app storefront. It’s a platform through which you manage your devices, apps, locations and so forth.
While the Android Open Source Project (AOSP) provides common, device-level functionalities such as email and calling, GMS is not part of AOSP. GMS is only available through a license with Google and delivers a holistic set of popular apps and cloud-based services. Note that GMS apps can vary based on country availability and requirements. 2