In many family law cases, it becomes necessary to obtain information from the opposing party. Since you are, in effect, "discovering" facts about the other side's case, this process is called discovery. Gerald O. Williams of the Minnesota Divorce and Family Law blog wrote the following article which compares formal vs. informal discovery:
Discovery is the process of obtaining and providing information in the family court proceeding. The formal process of discovery includes interrogatories; requests for production of documents; and depositions. Interrogatories are questions or demands for information that must be answered in writing. Requests for production of documents involve providing copies of documents such as bank statements, asset verifications, tax returns and real estate records. Depositions are oral proceedings in which the person answering questions is providing sworn testimony, and the questions and answers are placed on record by a court reporter.
In many cases, it is not necessary to proceed with formal discovery, if there is enough cooperation between the parties and their attorneys. In divorce cases, the parties are required by law to disclose relevant information so as not to defraud each other (or the court) in arriving at a fair and equitable settlement. Consequently, it is often possible to streamline the exchange of information in a manner that is mutually beneficial and economical.
Informal discovery typically happens by letter, or by meeting in person, or both. The person providing information furnishes sufficient detail and supporting documentation in a manner that obviates sworn testimony at a deposition. The person on the receiving end, in following up and requesting additional detail or additional documentation, often does not need a great deal of the information that would be part of the formal discovery process. The exchange of information is tailored to the specific claims and relevant circumstances of the case, instead of the "fishing expedition" that the formal discovery process is characterized as by many lawyers and judges.
Source: "Formal Discovery Versus Informal Discovery" by Gerald O. Williams, published at hisMinnesota Divorce and Family Law blog.