Proceedings taken during the course of, and incidental to a trial; a housekeeping order, one that relates to process of the trial as opposed to the substance of the pleadings.
Examples include procedures or applications made which are to assist a case in preparing its case or of executing judgment once obtained (eg. garnishment or judicial sale).
These decisions intervene after the start of a suit and decide some intervening procedural issue other than the final decision itself.
For example, if a plaintiff dumps upon a defendant a vague or incomplete statement of claim such that the defendant cannot really make out the case against him or her, the defendant can seek an interlocutory order against the plaintiff that the plaintiff provide more information or detail in the statement of claim.
Another frequent interlocutory application occurs during the discovery process where one side is obliged to provide the other with all relevant documents but the receiving party believes that one or more relevant documents are being withheld. An application can be made to the court for an interlocutory order that the withholding party fully disclose all relevant documents to the other side.