Who are and what rights do "interested parties" have in a civil law suit?

the rights that parties have when they are named interested parties in a cause of action

A party of interest in a suit would indicate that person/company/entity would stand to gain or lose something depending on the outcome. They can testify in or submit evidence to the court.

The interested paries are the plaintiff and the defendant. They have a right to present evidence to prove their case.

As you may learn from the law soon enough, there are plaintiffs (complainers) and respondents (answerees) just like any other case that must be "presented" correctly, interested parties could be witnesses, or others effected by the decision of the case.

Interested parties are people who have some kind of legal interest in the law suite; for example if your house is being put up for Sheriff Sale an interested party might be a contractor who did work on the house , but was never paid, and then put a lien on the property...he might have some rights or might be able to recover some of his loss when the property sells... Even though he is not named specifically in the caption of the law suit he might still have an interest in the outcome of the suit

Plaintiffs and defendants are not interested parties in a suit. Interested parties are parties outside those two entities who stand to be affected by the outcome of the suit.

"interested parties" are anyone who could be connected to a civil lawsuit or civil case. If you are an "interested party" you will receive copies of all pleadings and be notified of court dates. If you receive notice you should appear and find out how you are connected to the case and if you need to hire your own lawyer.