When someone files a complaint against you, you must respond otherwise receive a default judgment against you. However, you have options in how to respond. The primary of which is to answer the complaint. But, if the complaint filed fails to plead sufficient facts to win on a claim they are suing on, or they are in some other way precluded from filing the claim, your best course of action is to file a demurrer.
A demurrer is a motion that informs the court that even if you take every fact alleged by the plaintiff to be true, the plaintiff still can’t win. This can occur for several reasons. Whether the statute of limitations has already run, or the plaintiff failed to plead sufficient facts to satisfy the elements of the claim.
Recently, the legislature mandated that prior to filing a demurrer a defendant must meet and confer with the plaintiff. This means that before filing the demurrer you now have to inform the plaintiff of the faulty nature of the complaint. A result of this is that if the defect of the complaint can be fixed, it likely will be fixed by the Plaintiff as the Plaintiff is allowed to amend their petition without leave from court prior to an answer being filed.
If the defect is not or cannot be fixed, then you can file your demurrer. Once the demurrer is filed you will get a hearing date to argue the merits of the demurrer. If you win the court will then decide whether to deny or grant the demurrer, and if they grant the demurrer they will make a ruling to either give leave to amend (allow the plaintiff to refile the petition) or without leave to amend (they will have to file an entirely new case).