"Help" means helping a teammate accumulate free lives. You can help every player once for every life request. When a player gets the 5 lives they requested, the asking lives bar disappears from the chat. For each life you give another player, you receive 1 gold coin.
In the “My Team” section, you can see how many times a player on your team has helped other teammates. This counter will reset weekly, so you can track who has been actively helping in your team!