To interactively display information from the web INSIDE a dashboard, you can use a URL action with a web page object.
For example, you might have a dashboard that shows profits by country. In addition to showing the profit data in your dashboard, you also want to display supplemental information about the countries from a web site.

From the official documentation:
When you have a view with a large amount of data you might want to explore your data interactively and highlight a specific mark or group of marks while still maintaining the context of where those marks show in your view.
To do this you can turn on the Highlighter for one or more discrete fields that are included in your view and that affect the level of detail Example - Here we just want to focus on Public Affairs college dimension, but don't want to filter out or remove the rest of the data:

Note that filtering is not the correct option since that would REMOVE the data that doesn't match the filtering criteria.

GDP / Population = GDP Per Capita

Here Sum is a function, / and + are operators. On the bottom there are comments.

When we create a reference line, we get the following 3 options for the scope:

Pretty common question on the Tableau Desktop Specialist exam.
1) First, lets create Sheet 1. For this, drag sport to the Row shelf, and Weight to the Text mark in the Marks shelf. Change its aggregation to Average:

2) Now, for sheet 2 - Drag nationality to the view, and gold to the size mark in the Marks shelf.
NOTE: Depending on your version of Tableau , you may need to assign a Geographical role to the nationality column first as follows:


3) Now, let's create a dashboard, and use both these sheets in it:

4) Now, for the most Important step, use SHEET 2 AS A FILTER FOR SHEET 1 as follows:

Now simply click on Russia in Sheet 2, and Sheet 1 will automatically update as follows: