Here is a ready reckoner to help you through some of the terms so you have a better idea of what you are buying or declining. Just initial here and here please.....
CDW – Collision Damage Waiver is in effect insurance against damage to the car you are hiring occurring under some circumstances. It will often not cover fire, theft, damage to tires, loss of keys, damage to windscreens, fuelling with wrong fuel and damage to the underside of the car. It is not actually insurance but is a waiver from the hire car company of their right to sure you for damaging their car.
ERI – Excess Reimbursement or Excess Reduction Insurance reduces the amount you will have to pay if you return the hire car damaged.
ESP – not extra sensory perception in this case but Emergency Sickness Protection. This is only offered to non-US nationals and covers some hospital bills for some illness. All of this should be covered on your travel insurance.
LDW – Loss Damage Waiver is a term used specifically in the US and 
is a more comprehensive version of CDW. It generally covers damage to the rental
car caused by an accident, fire, theft or vandalism.
PAI– Personal Accident Insurance will pay out relatively small sums for accidental death or medical expenses in connection with an accident normally to the renter and passengers. Sometimes the renter and their immediate family are covered whether the accident is in connection with the hire car or not. Passengers are normally only covered in connection with some type of accident involving the car.
PEI – Personal Effects Insurance. This is insurance for personal effects usually of the renter and their immediate family only.
PPI/ PPP – Personal Protection Insurance or Plan is some combination of Personal Accident or Personal Protection Insurance.
SLI- Supplemental Liability Insurance is additional third party liability insurance which increases the cover should you damage someone else’s property or injure someone in an accident that is your fault. This can also be called Additional Liability Insurance (ALI).
UMP – Uninsured / Underinsured Motorist Protection. This cover will pay out for injury sustained to the driver and passengers of the hired vehicle if it is hit by a driver with insufficient or no insurance or a hit and run case.