Dried strips or a powder made from red seaweed. Boiled and cooled, it sets into a firm jelly for desserts; soaked strips are also tossed with cucumber and vinegar as a cold dish.
When making jelly you can use agar instead of gelatin.
Tips
memory
琼 originally means 'fine jade' - a poetic name for a clear gel. 脂 means 'fat / grease'. Together: 'jade-like gel'. Useful to remember it sets firmer than gelatin and is plant-based, so vegetarian-friendly.