Unisexual: In most of the animals including humans, male and female reproductive organs are in different individuals. Such animals are called unisexual.
Bisexual: In some animals like tapeworm, liver fluke, earthworm, leech, etc., the male and female reproductive organs are found in a single individual. Such organisms are called bisexual (hermaphrodite). The flower may be unisexual (e.g., papaya, watermelon) when it contains either stamens or carpels. and bisexual (e.g., Hibiscus, mustard) when it contains both stamens and carpels.