Variables are a way of categorising data. They can be arbitrary but in order to describe data well they must be carefully and purposefully chosen.
An example of a variable is one commonly used on the Seer platform, called “State or Territory”. This is a location based variable that can be configured to convey that the data being collected is associated with specific States or Territories. The variable “State or Territory” will have a set of Categories like “New South Wales”, “Victoria” and so on (for data in Australia).