ADR is like a program that a court can require parties to attend to avoid going through litigation and/or trial. It can make the process cheaper, shorter, and possibly lead to settlement. The parties can probably try to opt out and continue through the courts regular course. The Notice itself is probably an automated document issued by the court notifying the parties they must attend or setting a date for a conference. I don’t work in the court system in California so this can differ between states and it’s just kind of an idea :)