Coins are an in-game currency. They're used for several things:

• buying boosters;
• buying additional moves while playing levels;
• refilling lives.

You can receive coins:

• for beating levels;
• for completing game days;
• for restoring areas on the farm;
• from the in-game characters as a token of their gratitude for your help, or for other achievements;
• for updating the game;
• through in-game purchases available for real money.