Provides application programming interface through Java/Dalvik virtual machine (DVM)
Dalvik hides OS complexities from app programmer, who can write apps in (best programming language :-) ) Java
Jxyz can be ported, or already ported, to run on DVM
Provides utilities and libraries like modern web browser, media support, GSM telephony and lot of other things like OpenGL, Location support.
My thoughts – Android is Linux based platform, customized to run on mobile/handheld devices which have limited processing power and memory. These devices will run many apps/utilities, one of them being GSM telephony.