A CS2 sticker is a small image you place on a weapon skin. Stickers come from sticker capsules, Souvenir packages, operations and some drops. Once applied they stay with the weapon, can be moved a little on the surface, and can be scraped down in steps or removed fully, which destroys the sticker.
Most stickers cost very little. A few, mainly team and player stickers from early Majors and special finishes like Holo, Foil and Gold, are expensive on their own and add real value to a weapon when applied.
How many stickers can you put on a CS2 skin?
A weapon skin holds up to five stickers, and since CS2 you can place them almost anywhere on the weapon rather than in fixed slots. Knives and gloves cannot take stickers. Each sticker on an item shows in the inspect view and on marketplaces, which is why sticker placement has become part of how traders present a skin.
A sticker on a weapon is not the same as a sticker in your inventory. You cannot take it off and sell it. That makes the applied sticker's value hard to recover, and it is why a stickered skin usually sells for less than the skin plus the unapplied stickers would.
Do stickers add value to a skin?
Sometimes. Buyers pay extra for a clean set, meaning matching stickers in a neat layout on a fitting skin, and for rare stickers on any skin. They rarely pay full price for the stickers themselves. A common rule of thumb is that applied stickers add a fraction of their market value, and mixed or scraped stickers may add nothing.
Check the sticker names and wear on the inspect link before buying. Sticker wear is separate from skin float, and a heavily scraped rare sticker is worth much less than a fresh one.