Django 中的“应用程序”是什么

什么是Django中的“应用程序”？

$ python manage.py startapp blog

python
from django.db import models
class Post(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)

python
from django.shortcuts import render
from .models import Post
def post_list(request):
    posts = Post.objects.all()
    return render(request, 'blog/post_list.html', {'posts': posts})

html
{% for post in posts %}
    
{{ post.title }}
    
{{ post.content }}
    
Created at: {{ post.created_at }}
{% endfor %}

python
INSTALLED_APPS = [
    ...
    'blog',
    ...
]