When you enter a chat conversation with a pal, you'll see a green menu bar below.
They consist of four buttons:
Text mode lets you send text messages and emoticons to your pals.
Voice mode lets you record and send audio messages to your pals.
Phrasebook mode guides you to learn and speak a language through everyday words and phrases, especially if you're not familiar with it.
Media mode lets you send or take pictures and send them to your pals.