What is Django custom manager and QuerySet?

Custom managers and QuerySets encapsulate reusable query logic in the model layer: Custom QuerySet: class ArticleQuerySet(models.QuerySet): def published(self): return self.filter(is_published=True) def by_author(self, user): return self.filter(author=user) def with_stats(self): return self.annotate(comment_count=Count("comments"), like_count=Count("likes")) def recent(self): return self.order_by("-published_at")[:10]. Custom Manager: class ArticleManager(models.Manager): def get_queryset(self): return ArticleQuerySet(self.model, using=self._db) def published(self): return self.get_queryset().published() def for_homepage(self): return self.published().with_stats().recent(). Apply to model: class Article(models.Model): ... objects = ArticleManager() # Replace default manager. Chaining (from_queryset): ArticleManager = models.Manager.from_queryset(ArticleQuerySet) class Article(models.Model): objects = ArticleManager(). Usage: Article.objects.published() Article.objects.published().by_author(user).with_stats() Article.objects.for_homepage(). Multiple managers: class Article(models.Model): objects = models.Manager() # Default all articles published = ArticleManager() # Published only. Use: Article.published.all(). First manager is default — affects admin and related lookups.