These "xxxStart", "xxxEnd" attribute is to support RTL(Right to Left) layout in some locales.
Such as
android:paddingStart
android:paddingEnd
android:layout_marginStart
android:layout_marginEnd
...
You can see more here about it.
In normal(left to right) layout, "xxxStart" means "xxxLeft" and "xxxEnd" means "xxxRight".But in Right to Left layout, "xxxStart" means "xxxRight" and "xxxEnd" means "xxxLeft".
But RTL is only supported on sdk 17 and higher.
To support lower sdk, you can use "android:layout_marginStart" along with "android:layout_marginLeft". At the lower sdk devices, "android:layout_marginLeft" will be used.
