What is an ActiveRecord query interface?

ActiveRecord provides a chainable query interface that builds SQL lazily. Key methods: User.all, User.find(id), User.find_by(email: 'a@b.com'), User.where(active: true), User.order(:name), User.limit(10).offset(20), User.select(:id, :name), User.joins(:posts), User.includes(:posts), User.count, User.sum(:amount). Queries are not executed until results are needed (lazy loading). to_sql returns the generated SQL string for debugging.