what is from django.db.models import F code example

Example: from django.db import models

from django.db import models

class Person(models.Model):
  	"""
    	This class creates a new table with 
        the name of your application and that class name. 
        The fully qualified name of the table 
        will be "appName_className". 
        Also, two fields with data type char will be 
        created: first_name and last_name.
    """
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)