Ancillary jurisdiction enables a court to hear claims that are not within its original jurisdiction but are related to a case already before it. It allows for the efficient resolution of all disputes arising from the same situation without the need for separate proceedings.
For example: To illustrate, if Party A sues Party B for breach of contract in federal court, and Party B has a related claim for indemnification against Party C, the court can use ancillary jurisdiction to hear the indemnification claim even though it is a state law matter.