ISO/IEC 15504, also known as SPICE, is an international standard for software process assessment. It defines a framework for assessing processes based on a process reference model and capability levels. Processes are divided into categories and each process is assessed against attributes to determine its capability level on a scale of 0 to 5. ISO/IEC 15504 provides guidelines for conducting assessments through steps like planning, data collection, and reporting results. Assessors require training and experience to perform assessments competently. The standard can be used for both process improvement and determining a supplier's process capabilities.