Import sqlalchemy import *,SSHOperator and BranchPythonOperator

I am writing a python script. On top tried impo开发者_StackOverflow中文版rting some modules from the packages. I am confused with these lines. Can some one explain in simple terms, the "Meaning" of these lines?

I have just written these lines of code. I am stuck at understanding the difference between 'variable' and 'Variable' with a capital V.