Tokens are the currency of Conversifi. One token is spent following the completion of a learning session, and one token is earned following the completion of a coaching session. You can check your token balance in the upper-right hand corner of the screen. If you have questions about your balance, the best place to start is the History tab in the Tokens link, which shows all the tokens you've earned, bought and spent.
You will need at least one token to begin a lesson as a learner, so if the option to practice your target language is invisible on your screen, you'll need to coach a lesson first or buy tokens.
To purchase tokens via PayPal, select the Tokens link on the sidebar to the left. Prices for tokens are visible in the Buy Tokens menu.