PingCastle is a Active Directory Security Assessment Tool designed to quickly assess the Active Directory security level with a methodology based on a risk assessment and maturity framework. It does not aim at a perfect evaluation but rather as an efficiency compromise.
The risk level regarding Active Directory security has changed. Several vulnerabilities have been made popular with tools like mimikatz or sites likes adsecurity.org.
CMMI is a well known methodology from the Carnegie Mellon university to evaluate the maturity with a grade from 1 to 5, PingCastle has adapated CMMI to Active Directory security.