Validators are used to prevent SQL Injection attacks in which malicious users can enter their own SQL commands into the application through a URL parameter and execute them on behalf of other users.
Validation can be divided into three categories:
1. Prospective Validation is the first step in the validation process.
2. Concurrent Validation is the second step in the validation process.
3. Retrospective Validation is the third step in the validation process.
Validation ensures that the provided text is in the correct format (e.g., email@example.com for email) and that the text meets the requirements for a valid entry (e.g., the email address isn't already registered, or the password meets the criteria).