Wrongful dismissal is a contractual claim. This arises where an employee has been dismissed and the employer has failed meet the contractual obligations to the employee. For example, the employer has failed to give the employee his notice.
If you have committed an act of gross misconduct and your employer has terminated for that reason, then you would not be entitled to receive notice or payment in lieu of notice. However in any other circumstances, in order to terminate your employment, your right to notice means your employer must either allow you to work out your notice or make a payment in lieu of notice (garden leave). If you have been wrongfully dismissed, you are under a duty to mitigate your loss.