An Android emulator is software which simulates the functionality of an Android device running the Android OS
BlueStacks is a software platform which allows you to run Android apps on Windows and Mac, without the need of an Android emulator
"Yes some functionality possible only on device but you can try also bluestacks app player which has more possibilities than android-emulator"
from question "How to test iosched 2012?"
"2 if your host machine laptop doesn t have more ram then you might want to find alternative android-emulator like genymotion bluestacks which takes less memory than android-emulator"
from question "Android emulator hangs forever at boot time"
"This android-emulator works better than bluestacks"
from question "Running Instagram on AVD"
"In xda-forums i read about memu - most powerful android-emulator for pc better than bluestacks"
from question "Emulator error: This AVD's configuration is missing a kernel file"