Good question. When the plant begins to flower, the difference between male and female becomes obvious. Females develop pistils (light-coloured furry tentacles) to try to catch pollen, and form a seed. Male flowers develop pollen sacs which open up after a few days to release pollen (yellow dust).
https://hive.blog/cannabis/@drutter/uh-oh-another-male
Males don't produce much medicine, so unless you want their pollen (to make your females produce seeds) it is best to identify and remove them from medicine gardens.
Sometimes seeds are "feminized" which means the plants that grow from them are female. If you don't want any males that can be a big advantage. My seeds are NOT feminized, so I will have to be watching for males. That doesn't happen for several weeks, though.
thank you