What Tableau is for

Tableau lets somebody explore data without writing queries. You connect it to a source, drag fields onto a canvas, and it draws the chart.

Who it is for. Analysts producing dashboards for people who will never open a database, and business users who need to answer their own questions rather than requesting a report and waiting three days.

Where it fits against the alternatives. Excel is fine up to a point and becomes unmanageable with large data and recurring reports. Python gives complete control and requires code. Power BI is the close competitor and is common wherever an organisation is already on Microsoft. Looker Studio is free and lighter. Tableau is strong on visual exploration and is widely asked for by name in analyst job adverts, which is a practical reason to learn it.

Tableau Public is free and publishes your work openly, which makes it excellent for learning and for building a portfolio and unsuitable for anything confidential. Tableau Desktop and Server are paid.

Two ideas that explain most of the interface.

Dimensions and measures. A dimension is something you group by: region, product, month. A measure is something you aggregate: sales, quantity, hours. Tableau decides which is which on connection and it sometimes decides wrongly, and a great deal of early confusion is a field classified as the wrong one.

Rows and columns shelves determine the structure of the chart, and everything else adjusts it.