高档 (gāo dàng) describes products, services, or places that are high-end and upscale, often in commercial contexts (e.g., 高档手机, 高档酒店). It is more specific to luxury goods than 高级 (gāo jí), which can also mean 'advanced' or 'senior' (e.g., 高级经理). 高端 (gāo duān) is very similar but often used for technology and market segments.