Validations provide a way to test user input and ensure that the data provided by the user is clean, correct, and useful. Validation scope may be as simple as checking whether the field is empty, or provide complex checks including powerful regular expressions and custom validations.
When to Use
Validations are recommended when a user is expected to follow an unfamiliar sequential process (inexperienced user or a rarely used process).
For more details refer to:Creating Validations