Complex sentence: An alternative runtime environment called Android Runtime (ART) was included in Android 4.4 "KitKat" as a technology preview, replaced Dalvik entirely in Android 5.0 "Lollipop".
Split into simpler sentences: An alternative runtime environment called Android Runtime (ART) was included in Android 4.4 "KitKat" as a technology preview. ART replaces Dalvik entirely in Android 5.0 "Lollipop".