getTranslateTransform

This method exists only on Animated.ValueXY instances. The documentation explains it here http://facebook.github.io/react-native/docs/animated.html#gettranslatetransform.

This is a helper that just saves you some code. The equivalence of what it generates is something like so:

this._animatedValue = new Animated.ValueXY();

transform: [
  {
    translateX: this._animatedValue.x,
  },
  {
    translateY: this._animatedValue.y,
  },
];

That would be provided to an Animated.View or other Animated component.

<Animated.View
  style={{
    transform: [
      {
        translateX: this._animatedValue.x,
      },
      {
        translateY: this._animatedValue.y,
      },
    ],
  }}
/>

But with the helper method you would only need to do

<Animated.Value
  style={{
    transform: this._animatedValue.getTranslateTransform(),
  }}
/>

Why use Translate

Translate allows for us to change the position of a component regardless of it's current layout. When you use getLayout, the component must be set to position: 'absolute'; however, a compnent you would like to move may not necessarily be absolutely positioned.

Further more, if you do have a component positioned absolutely, you may want to move the component but not affect it's layout. An example would be in the case where you have a full screen modal using {position: 'absolute', left: 0, right: 0, top: 0, bottom: 0}, but would like to animate it off the screen.

This is where you could use the translateX/translateY to move it without affecting the layout. If you are interested you can read more about it on my blog here: http://browniefed.com/blog/2015/10/18/react-native-easy-overlay-modal-with-navigator/.