What is a written warning?

It is a warning given by management that an employee is not meeting their expectations, or due to a certain behavior, why improvements are desired in these areas. Here is a specific explanation of what needs to be improved, and a deadline for when this must happen.

Why is it important?

A written warning is important because it can help management correct an employee who has not lived up to expectations. Should an employee fail to correct their behavior within the given deadline, a consequence will arise. If the employee is a salaried employee, it is a requirement that they receive at least one written warning before termination.

Examples of what it can contain

Who are the parties
A specific description of what the problem is
A specific description of what the employer expects from the employee
A deadline for when the employee will change
A specific description of what consequences this may entail
Signature of both parties