I'm assuming you are either the husband or wife in this case. It's just a type of document to have you appear at a certain place and time - usually a court appearance. They just want to make sure you show up. If there is a reason you can't or shouldn't be there, then I'd suggest you talk to an attorney if you don't already have one - if you do have one, then talk to them about why they are requiring you to be there.
Good luck with your situation. The above is general information and not legal advice.
You may receive notice such as you mention in the mail. If you are personally served then if you do not come to court when the document requires, a warrant may be issued for your attendance before the judge to explain why.