An MSC is a proceeeding scheduled close to the trial date where any issue still in dispute before trial gets discussed and, hopefully, settled at this conference. Sometimes MSCs are held by your trial judge and more often, held by another judge appointed for this purpose.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
An MSC is exactly what it says: a conference, with a judge or mediator, in a final effort to settle either the entire case, or as many issues as possible, before the matter actually proceeds to a trial.
To have a meaningful settlement discussion with he parties, the judge or settlement officer needs some information as to what issues are unresolved, and what each party's position on that issue is. Most counties have requirements that such information be prepared and provided to the court, and the other party in advance of the actual conference date.
There should be a set of rules or orders which lay out, in detail, what you need to bring, file, and serve on the other side at, or before, the MSC. See http://www.occourts.org/directory/local-rules/local-rules-of-court/.
When the judge in your matter SET the MSC, he or she may also have made additional orders.
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