A span that supplies additional meta-data for the associated text intended for text-to-speech engines. If the text is being processed by a text-to-speech engine, the engine may use the data in this span in addition to or instead of its associated text. Each instance of a TtsSpan has a type, for example TtsSpan.TypeDate or TtsSpan.TypeMeasure. And a list of arguments, provided as key-value pairs in a bundle. The inner classes are there for convenience and provide builders for each TtsSpan type.

[Android Documentation]