Classification codes are a very broad way that articles are tagged in ABI/INFORM. It can be useful to do a search that combines a classification code (or codes) with keywords or subject terms.
Codes for HR Issues:
6000 HR Management
6100 HR Planning
6200 Training & Development
6300 Labor Relations
6400 Employee Benefits & Compensation
6500 Employee Problems
Example:
nurses AND CC(6400)
This would find articles with the keyword nurses that were also tagged as related to Employee Benefits & Compensation issues.