컵(keop)
A general vessel or container used for drinking beverages
When to use
Drinking beverages at home, Serving drinks at restaurants, Disposable drink containers
The nuance
Used typically at home or restaurants for drinking; does not have insulation and is not designed for portability.
텀블러(teom-beul-reo, teombeulreo)
A portable beverage container with insulation to keep drinks hot or cold
When to use
Portable for commuting, During outdoor activities, When insulation is needed
The nuance
Used for carrying drinks while maintaining temperature, suitable for office, outdoor activities, or travel.