Tableau has many inbuilt string functions that can be used for string manipulations like concatenation, replacement, finding the character in a string etc. For example if you want to find the sales for only those cities which contains "vill" as a sub string. So for that below are the steps:
Step 1: First drag and drop city and Sales fields in rows and column shelf as shown below
Step 2: Create a calculated field by using CONTAINS (String function) as shown below
Step 3: Once you create and rename the calculated field then drag and drop it in filters card, then you will see a new pop up window. select True from this window and click on apply.
Step 4: Now you will see only those cities which contains "vill" sub string in their name.
If you want to learn more about calculated field and Tableau functions in detail then you can check learn tableau or get indepth knowledge about this field through Tableau Certification Course by Intellipaat.