how is levelling different from tilling? what is the significance of the processes mentioned?

Tilling is a process of loosening and mixing the soil so that it becomes easy to sow the seeds and levelling is a process of equalising the surface of the soil after tilling so that no lumps are left in the soil.
Tiling is done to aerate the soil and to mix the nutrients of the soil and levelling is done so that no lumps will left in the tilled soil as they can hinder the growth of plant.