"Juice is a beverage."
Translation:Juice er en drikk.
Nothing but the spelling. They're both accepted variants, with 'juice' being the most common.
Those are grammatical genders. Nouns either use one or the other. It's just like Spanish, French, or most of the other European languages.
If you ask a Norwegian for 'saft' then they will assume you want a cordial/squash kind of drink, basically a mix of fruit/berry concentrate and water.
appelsinsaft = orange squash/cordial (water + concentrate)
appelsinjuice = orange juice
We do however often refer to the liquids/juices inside plants, fruit, berries, and even meat as 'saft' when they're not drinks. Typically when cooking:
"Tilsett saften av en sitron, og rør godt."
"Add the juice of a lemon, and stir well."