The singular form dtype is used to check the data type for a single column. And the plural form dtypes is for data frame which returns data types for all columns. Essentially:
For a single column:
dataframe.column.dtype
For all columns:
dataframe.dtypes
Example:
import pandas as pd
df = pd.DataFrame({'A': [1,2,3], 'B': [True, False, False], 'C': ['a', 'b', 'c']})
df.A.dtype
# dtype('int64')
df.B.dtype
# dtype('bool')
df.C.dtype
# dtype('O')
df.dtypes
#A int64
#B bool
#C object
#dtype: object