In the last chapter, sorting and filtering was explained. Sorting lets site builders specify what order their data lists should be in. Filtering lets site builders select just a portion of a large list, such as the Tiny House page that selects properties of less than 500 square feet from the total list of available properties. Exposed filters allow visitors to select the values or ranges of values that are most interesting to them, making the lists of data more interactive and useful.

Filters require the site builder to select the values or expose the filter to allow the visitor to select the values. As a result, it is common to see a single view with a dozen displays, each with a filter or two set to specific values, such as a neighborhood. There is a better way that allows Drupal to take a value from the URL or use information gathered from what page is displayed to filter results. This capability is called contextual filtering. Even though contextual filters...