"Dec page" is short for declarations page, it's the front page of your insurance policy that shows what coverages you have. If someone else's lawyer is asking you for this, don't comply unless advised to do so by your insurance company or your attorney. If YOUR lawyer needs it, you can of course give it to him.
"Subrogation" refers to what happens if you are in an accident that is not your fault, but you claim the damage to your own insurance under your collision coverage, and let them pay for it. Subrogation is when your insurance company then files a claim with the at-fault driver's insurance to be reimbursed for whatever they spent for the accident, and usually your deductible and any out of pocket expenses at the same time.
Subrogation can also refer to your health insurance seeking reimbursement for money that IT spent on your behalf for auto-accident-related medical bills, if you receive a settlement from the at-fault driver. They must be paid back before you get to keep any part of the settlement.