Recommendation systems are extremely powerful tools for improving user experience, managing a large catalogue, and converting to sale. They is particularly useful when your products or services have clear target markets with discrete metrics to identify them. They can be automatic, collecting information from the user's activities, purchasing, or browsing history. Think of Amazon's 'based on your purchase history' feed of products, or Youtube's recommended videos for you to watch. If such data isn't available, recommendations can also be made by collecting visitor details through a quick and simple questionnaire or webform, which then recommends the products or services that are mostly likely to fulfil their needs and convert them. Examples of these include estate agents, travel agents and train booking services.