An androecium is called the male reproductive organ of flower because it produces male reproductive cell called pollen grain.

Those flowers which have only stamen are called staminate flower. It doesn’t contain pistil. It is also called male reproductive flower. Similarly, those flower which have only pistil are called pistillate flower. It doesn’t contain stamen it is also called female reproductive flower.

Those plants which bear flowers and reproduce by seeds are called flowering plants.
The first and outermost whorl of the flower is called calyx.
Calyx protects flower in its bud stage and also helps in its photosynthesis process.

The gynoecium consists of three parts. They are stigma, style and ovary.

Corolla attracts insects that help in pollination.

The difference between sepal and petal are:

S.N Sepal Petal
1. It is the green colored flower. It is the brightly colored structure next to the sepal.
2. A group of the sepals are called calyx. A group of petals are called corolla.
3. It helps to protect flower in bud stage and also helps in photosynthesis. It helps to attract insects and thus helps in pollination.

The difference between stamen and carpel are:

S.N Stamen Carpel
1. It is the male part of the flower.It is the female part of the flower. It is the female part of the flower.
2. It consists of three parts (a) filament (b) anther lobes (c) connective. It consists of three parts (a) stigma (b) style (c) ovary.
3. It produces grains. It receives pollen grain, produces fruit and seeds.