The auth-methodType is used to configure the authentication mechanism for the web application. As a prerequisite to gaining access to any web resources which are protected by an authorization constraint, a user must have authenticated using the configured mechanism. Legal values are "BASIC", "DIGEST", "FORM", "CLIENT-CERT", or a vendor-specific authentication scheme.
P.S. You will not see any vendor-specific questions on SCWCD exam. Just remember 4 standard values.
Java Platform, Enterprise Edition 6 Web Services Developer Certified Expert Exam Study Guide and Quiz Exam 1Z0-810: Upgrade to Java SE 8 Programmer Study Guide and Quiz