PURLs (personalized uniform resource locators) are dynamically generated web pages composed of relevant information specific to the target based on their unique data. They connect offline advertising like print ads to the web, allowing responses to be tracked. While PURLs enhance personalization and relevance, some criticize them for poor planning, unappealing offers, or lack of follow up. Best practices for PURLs include being clear, short, optimized for all devices, trigger-driven for both customers and sales, and dynamically updated based on user behavior.