The API version determines the oldest level of Android on which you App will run. Android SDK API version 8 is for Android 2.2 so your App will run on any version of Android from 2.2 up (including the latest version). Choosing an older version of the SDK means that it will run on older versions of Android (e.g. API version 3 will support Android 1.5 and up) while a newer version limits your Apps to later versions (e.g. API version 17 requires Android 4.2 - the latest). If you need something that only appears in later APIs, then you are limiting the range of devices on which the App will run. Version 8 is a good compromise since most Android systems will be running Android 2.2 or later so it makes the App runnable on most systems.