Hi Chef,
That is a good question! Please look into the screenshots and the description given below. This will help you understand the game better.

Cloche Icon on top of the Tables: This means that the Customer is waiting to be served.

Green tick mark on the Table:
This means that the Order is ready to be served. You need to serve your customers by dragging the Dishes to the Table.
Red dot mark on Shop icon: This means that you have unlocked something for your Restaurant. You can visit and see what you have unlocked.