Measures are numerical values that mathematical functions work on. For example, a sales revenue column is a measure because you can find out a total or average the data. Dimensions are qualitative and do not total a sum. For example, sales region, employee, location, or date are dimensions.
In Tableau, when we connect to a new data source, each field in the data source is either mapped as measures or dimensions. These fields are the columns defined in the data source. Each field is assigned a dataType (integer, string, etc.) and a role (discrete dimension or continuous measure).
Measures contain numeric values that are analyzed by a dimension table. Measures are stored in a table that allows storage of multiple records and contains foreign keys referring uniquely to the associated dimension tables.
While Dimensions contain qualitative values (name, dates, geographical data) to define comprehensive attributes to categorize, segment, and reveal the data details.