EXCELLENT means minimal wear such as light case scratches. GOOD means minor wear such as scuffs, light dents, light screen wear (not visible when powered on). FAIR means fully functional but with heavy wear such as multiple/moderate dents, heavy scuffs, or screen wear.

All accessories must be manufactured by Apple and in good condition.

Less than fully functional is defined as having a "Replace Now" or "Service Battery" message in battery information or less than 70% of its original capacity.

Examples include failing hardware, water damage, cracks, dents, etc.