There four icons at the top left represent free rewards you can collect regularly.

Chest: Awards random resources and items every half hour.
Present: Log in for seven days in a row. You can open a chest each day, with the rewards get better. However missing a day will reset this.
Paper and feather: Sign in bonus that gives better rewards for five days in a row.
Star: Displays daily quests that will reward you with points. The more points you get, the higher your daily rank, and the better the rewards.