Fundamental structure in Pandas is the DataFrame.
DataFrame can be thought of either as a generalization of a NumPy array, or as a specialization of a Python dictionary
DataFrame as a generalized NumPy array
If a Series is an analog of a one-dimensional array with flexible indices, a DataFrame is an analog of a two-dimensional array with both flexible row indices and flexible column names.
If some keys in the dictionary are missing, Pandas will fill them in with NaN (i.e., “not a number”) values