The word "Biology " is derived from Greek word ( Bios + logos).
Bios means life and Logos means study. Hence we can say Biology is the study of life and living organisms.There are various branches of biology.Some of them are given below

1.Botany ( Study of plants)
2.zoology ( study of animals)
3. Microbiology ( study of microorganisms)
4.Genetics ( study of genes)

By studying Biology we get to know how a cell is working, how it adapts , how it changes with time and external or internal stimulus. With the help of biology we get to know how a living creature is made up of, we get to know about the cellular structure. It is very important to know the cell sturcture and the behaviour of the cell for the people who wants to study medicine.Biology helps us to know how some of our behaviour matches with our ancestors.

I hope now you have a clear vision about biology.If you have any query , please feel free to ask.