This is a tool that allows you to preview how Hindi and Thai text will appear in Pokémon GO. While your phone, computer, and web browser most likely support the complex text layout needed to display Brahmic scripts like Devanagari and Thai correctly, Pokémon GO does not. Instead, the game uses modified fonts and encodings that allows the game's text engine to display the correct forms of characters.
To convert your text into the format used by Pokémon GO, tap the "Encode" button. (Hindi encoding is currently unavailable.) To convert text from Pokémon GO into a readable format, tap the "Decode" button.