PLPD is an acronym for Public Liability and Property Damage. This term was common to Michigan insurance for many years up to 1971 when the Essential Insurance Act was passed. Believe it or not, their term PLPD has been out of date for over 30 years.
However the term still lives on. Commonly this term refers to having the bare essential coverages to legally drive in Michigan.  This refers to a set of insurance limits that all automobile drivers must meet or exceed by state law. To many Michiganders PLPD means: cheap insurance, bare bones coverage, what I need to not get a ticket from the police.
Minimum State limits will not adequately protect you in the event of a lawsuit. To be adequately protected you should at least carry enough coverage to protect the loss of all your assets. By carrying minimum limits you are paying as little as you can but are at a high risk of losing everything you have.