Question

If there is gravity on earth than why don't the birds and clouds fall down? ​

Answer 1

For the same reason that you're able to walk up the stairs when you feel like it. A force is used that works in the direction opposite to gravity and exceeds it.

Answer 2

Birds don't fall down when they fly because their wings build lift when they flap them. Clouds don't fall down because the water particles that they keep are spread out for miles, so gravity has little effect on them.