User filters allow you to limit the data a user is able to view according to who the user is. Each user will only be to view the data/charts by what they have access to. This is a feature that is available on Tableau Server and Tableau Online. It's similar to setting up custom views on Tableau Server, and useful for the same reasons. It gives users access to what they want to see/what is most relevant to them.
You can set up a user filter on Tableau Desktop by connecting to a data source and creating a workbook. Select the worksheet you would like to apply the filter to. And then from the menu, select Server, Create User Filter. Choose the data field you want to filter the view by (E.G. region). Once you've selected the data field, enter the name of the user that you would like to apply the filter for. You can add multiple filters, and you can do this for different users.
Once you've created the user filter, it will show as a set in the data pane (left-hand side with the data fields). To apply the user filter, drag it into the filters shelf. To test the user filter, select a user from the lower-left corner on Tableau Desktop to view the data as they would see the data.