Consumer Grade is the bottom rung of the CS2 rarity ladder. Every weapon skin belongs to one rarity tier, and Consumer Grade sits below Industrial Grade, Mil-Spec, Restricted, Classified and Covert. The label on the item is white or light grey, which is why traders often just call these skins "whites". The Counter-Strike wiki lists the full grade ladder and colours.
Consumer Grade skins do not come from weapon cases. The item dataset shows every case starts at Mil-Spec, while Consumer Grade skins sit in map and themed collections that drop through the weekly Care Package and appear in Souvenir packages. Because they are common and cheap, most sell for a few cents, and many people never look at them twice.
Why do traders still care about Consumer Grade skins?
The main reason is trade-up contracts. A trade-up takes ten skins of one rarity and returns one skin from the next tier up. Steam Support's trade-up rules say the result is always one rarity higher than the inputs, so ten Consumer Grade skins become one Industrial Grade skin, and clever traders chain these steps to reach higher tiers for less than the market price. Since the inputs cost so little, a Consumer Grade trade-up is the cheapest way to learn how contracts work.
The second reason is volume. Consumer Grade skins move in huge numbers on the Steam Community Market, so they are a decent way to study how prices settle when supply is almost unlimited. Fees can eat the whole margin on items this cheap, so check the numbers before listing.
Are Consumer Grade skins ever worth money?
A few are. Some Consumer Grade skins from old or retired collections have low supply and get bought for trade-ups into desirable Industrial Grade outputs. Float value and pattern can also matter, since a Factory New copy of a rare collection skin is worth more than a Battle-Scarred one. Still, the ceiling is low, and most Consumer Grade skins will stay near the minimum market price.