Question

how can we identify good, healthy seeds from the damaged ones what is that method called?

Answer 1

by putting the seeds in a Beaker containing water.
the healthy seeds will sink and damaged one will float.

Answer 2

Put seeds in water if they are floating and some are sinked then the floating are the bad ones.
Another way which is used is the take benefit from wind which blows away the lighter seeds which are not good and heavier seeds settle down