1) "get" is a method of a python dictionary to fetch the value from a key. If the key does not exist in the dictionary, you can pass a default value as a 2nd parameter:

myDict = {'name': 'Odoo', 'work': 'ERP'}

# I will fetch the value of the key that does not exist in the dict
1) myDict.get('address', '') # if no address, return value passed in 2nd parameter

2) myDict.get('company_ref', False)

2) You can also fetch the value by simply passing a key:
Ex: myDict['name']

if myDict['name'] == False
# This means, if name is blank or has False as a value

I hope, this will help you at some point to clear your doubt.