 <p>A validation is a check that the value entered is legitimate for the context of its field (from technical perspective), for example: is 5 as a numeric value acceptable for Age(v.s. -5)?, while -5 is acceptable as Temperature for example.</p> <p>The business rule is more of a business perspective. It is a check that the values (that passed the validation) are acceptable by the policies and procedures of the business. E.g. the person who is allowed to register has to be a resident, and 18 years old or more..etc. The business rule might check one (or more) field(s) value(s), and might consult data stored in a database and/or do some calculation(s) to ensure that the value(s) pass the business rules.</p> <p>So, for the example posted above by hanna, the value 15 should pass the field validation (as it is a valid value for Age), but it will not pass the business rule check that the married person's age must be >15.</p>