Dimensions and measures

When you connect a data source, Tableau automatically separates fields into data roles: Dimensions and Measures. Dimensions and measures affect visualizations differently. Understanding their differences will allow you to build visualizations faster - and to correct the choices made by Tableau, if necessary, as it won't always choose the appropriate role.

Checking your fields' data types and roles when connecting to data will make your life much easier when creating visualizations, and will also allow Tableau to make better suggestions. In the end, Tableau is a very efficient program, but you remain the human in charge.