Dashboard - a collection of views shown in a single location where you can compare and monitor a variety of data simultaneously. 

Data Source - The underlying data that a Tableau  product is connected to. 

Repository - A folder located in your My Documents folder that stores workbooks. 

Workbook - A collection of one or more worksheets and dashboards. 

Worksheet - A single view of data. Each worksheet can be connected to a single data source. 

Dimension - A data field that contains qualitative data such as names, dates, or geographical data. It is typically a field that cannot be aggregated.

Measure - A data field that contains numeric, quantitative values that you can measure. 

Site - A collection of users, groups, and content (workbooks, data sources) that is separated from any other groups and content on the same instance of Tableau Server. It is a place for teams to publish data sources and workbooks to share with each other. NOT to be mixed up with website.

Visualization - also called viz, a graphical representation of information and data. By using visual elements like charts, graphs, and maps, data visualization tools provide an accessible way to see and understand trends, outliers, and patterns in data.