Answer 1

Probably you got that at Pandas.
'loc' accesses a row by its name,
'iloc' does the same with row number. Ex.

import pandas as pd
df = pd.DataFrame({'a':[1,2],'b':[3,4]}, index = ['first', 'second'])
#it creates two row, first and second
print(df.loc['first'])
print(df.iloc[0])
# both prints the same