There are a few different ways that a termination could be considered wrongful. Generally, it has to do with an employer breaking contract law, violating public policy, or discriminating against a protected class of employees.
For example, if you had an employment contract that stipulated you could only be fired for specific reasons, and your employer decided to fire you without cause, that would be considered a breach of contract and grounds for wrongful termination.
If your state has a law forbidding employers from firing employees who take emergency leave to tend to a sick family member, and you are fired after taking such leave, that would also be considered wrongful termination.
It can be a very difficult and confusing time when you are wrongfully terminated from your job. You may feel like you have nowhere to turn and that no one is willing to help you. But there are a few things you can do to try and get your job back or at least receive some compensation for what happened.