Tournament Coins: Tournament coins are awarded as gifts for the esteemed players to participate in the particular Tournament. Tournament coins are to be used towards the specific ongoing Tournament only, not for regular gameplay.
Regular Coins: Coins at the top left are your regular coin balance, which can only be used for regular gameplay. Regular coins can not be used to participate in the special Tournament. During the Tournament, tapping on of regular balance will show you a tooltip pop-up with tournament balance details.