android - Difference between a View's Padding and Margin

Padding is within the view, margin is outside. Padding is available for all views. Depending on the view, there may or may not be a visual difference between padding and margin.

For buttons, for example, the characteristic button background image includes the padding, but not the margin. In other words, adding more padding makes the button look visually bigger, while adding more margin just makes the gap between the button and the next control wider.

For TextViews, on the other hand, the visual effect of padding and margin is identical.

Whether or not margin is available is determined by the container of the view, not by the view itself. In LinearLayout margin is supported, in AbsoluteLayout (considered obsolete now) - no.