Tokens are used to unlock new puzzles from the Home screen.

In the current chapter, a crossword grid containing purple circles. Each circle represents a locked puzzle. The numbers in the circle is the token cost to unlock the puzzle. 

Unlocked puzzles stay available untim completed. When you have completed a puzzle, it will reveal a letter on the grid. Selecting it will allow you to review the puzzle, or replay it. 

The number of tokens you have available is shown bottom of the screen.