I heard about parameters when I was trying to complete my first ever dashboard, however, they seemed to me so mysterious that I didn't even try using them in my visualization - what a shame!
After todays morning session in Tableau Desktop, I feel like I started getting more of understanding how and when to use parameters.
Starting from the beginning, a parameter is a workbook variable like number, date, or string that can replace a constant value in a calculation, filter, or reference line. For example, you may create a calculated field that returns True if Sales is greater than £300,000 and otherwise returns False.
Why use parameters in your visualization?
Parameters allow user to change the content that appears on the workbook or dashboard. User can select or input a value, it gives the chance to dynamically modify values. Parameters make our dashboard more interactive. They apply to the whole data set, so they can be used across all the workbooks and dashboards.
When you decide to incorporate parameters into your view, you let viewers choose how they want to look at the data.