Pandas objects
At the very basic level, Pandas objects can be thought of as enhanced versions of NumPy structured arrays in which the rows and columns are identified with labels rather than simple integer indices. As we will see during the course of this chapter, Pandas provides a host of useful tools, methods, and functionality on top of the basic data structures, but nearly everything that follows will require an understanding of what these structures are. Thus, before we go any further, let's introduce these three fundamental Pandas data structures: the Series, DataFrame, and Index.
Groupby
In this section you will get the practical understanding on groupby function.
https://www.tutorialspoint.com/python_pandas/python_pandas_groupby.htm