What is the difference between Android margin start/end and right/left?

For left-to-right flow, start=left, end=right.

For right-to-left flow, start=right, end=left.

The "start" and "end" concepts were added in API Level 17, as part of Android 4.2's support for RTL layouts.

Android supports RTL layouts from API 17+ i.e., Android 4.2 (Jelly Bean).and when we make our layout to support both RTL and LTR then we can not use layout_marginleft and layout_marginRight there we use layout_marginstart and layout_maginend .