Example Concept: Custom dimensions in GA4 are user-defined attributes that you can use to segment and analyze data beyond the standard dimensions. For instance, you might create a custom dimension to track user membership levels (e.g., "Gold", "Silver", "Bronze") or specific event details like "Product Category". These dimensions are set up in the GA4 interface under Admin → Property → Custom Definitions and can be used in reports to gain deeper insights into user behavior.