Name the main entities in Django.

• Project: A set of configurations and applications for a website.
• App: A self-contained module for performing a specific task or a set of related functions. Contains models, views, URLs, and migrations.
• Models: Define the data structure. They are classes that inherit from django.db.models.Model, with each variable representing a database table field. ActiveRecord pattern.

  // models.py
  from django.db import models
  
  class Product(models.Model):
      name = models.CharField(max_length=100)
      price = models.DecimalField(max_digits=10, decimal_places=2)
  
      def __str__(self):
          return self.name
  

• Views: Functions or classes that handle HTTP requests, interact with models, and return HTTP responses (usually HTML pages).

  // views.py
  from django.shortcuts import render
  from .models import Product
  
  def product_list(request):
      products = Product.objects.all()
      return render(request, 'products/product_list.html', {'products': products})
  

• Templates: Files containing static HTML and special syntax for dynamic content (template tags and variables). Used by views to generate HTTP responses.

  <!-- products/product_list.html -->
  <h1>Product List</h1>
  <ul>
      {% for product in products %}
          <li>{{ product.name }} - ${{ product.price }}</li>
      {% endfor %}
  </ul>
  

• URLs: Map URLs to views. Defined in urls.py files.

  // urls.py
  from django.urls import path
  from . import views
  
  urlpatterns = [
      path('products/', views.product_list, name='product_list'),
  ]
  

• Forms: Handle user input. Provide classes for creating HTML forms, validating data, and saving to models.

  // forms.py
  from django import forms
  from .models import Product
  
  class ProductForm(forms.ModelForm):
      class Meta:
          model = Product
          fields = ['name', 'price']
  

• Migrations: Changes to the database schema based on models. Managed with makemigrations and migrate commands.

These entities work together in a pattern similar to MVC, where Models are data, Views are request handling logic, and Templates are the presentation layer (UI). Django is often described as MVT (Model-View-Template).