Explanation
Remember that dragging a discrete value to colour creates distinct colours for each item whereas dragging a continuous value to colour creates a gradient. ( Same for Map ) From the official documentation:

Explanation
From the official documentation, the following are the major advantages of using Tableau Data Extracts:

From Tableau 2020.2 onwards, .hyper is the recommended way since it is faster than .tde!

Explanation
Using the Sample superstore as a reference:
1) Let's plot a bar chart showing SUM(Quantity) for each Segment:
2) Right click on the x-axis (Segment):
Notice we don't have an option to edit the axis, only header. This is because only continous values form the AXIS.
3) Similarly, right click on the y-axis (Quantity):

Now we have the option to edit BOTH the axis and the header.

Explanation
You don't need to know ANY programming language to use quick table calculations!
Follow along with the steps below to learn how to apply a quick table calculation to a visualization:
1) Open Tableau Desktop and connect to the Sample-Superstore data source, which comes with Tableau.
2) Navigate to a new worksheet.
3) From the Data pane, under Dimensions, drag Order Date to the Columns shelf.
4) From the Data pane, under Dimensions, drag State to the Rows shelf.
5) From the Data pane, under Measures, drag Sales to Text on the Marks Card.
6) From the Data pane, under Measures, drag Profit to Color on the Marks Card.
7) On the Marks card, click the Mark Type drop-down and select Square.

The visualization updates to look like this:

Apply the quick table calculation
1) On the Marks card, right-click SUM(Profit) and select Quick Table Calculation > Moving Average.
Note: You can only perform quick table calculations on measures in the view.
A delta symbol appears on the field to indicate that a quick table calculation is being applied to the field. The colors in the visualization update to show the moving average of profit across the years.

Explanation
You can add a reference line to any continuous axis in the view.
To add a reference line:
Drag Reference Line from the Analytics pane into the view. Tableau shows the possible destinations. The range of choices varies depending on the type of item and the current view.
In a simple case, the drop target area offers three options: