Stickers are the coloured pieces of paper on the puzzle that sit on each and every piece of the puzzle. They are applied with extremely high precision and determine the colour of the side of the piece they are applied on. “Stickerless” cubes are puzzles that don’t have stickers, but instead have their plastic pieces coloured from manufacturing.
They are available for many different puzzles, such as 2x2, 3x3, Pyraminx, Square-1, 4x4, Ghost Cube, 7x7, etc. They are usually needed when the current stickers peel off due to wear over time. They can be a great solution, especially in terms of saving money instead of buying an entirely new puzzle.
Some stickers have been discontinued, but most of them are available in this giant collection of stickers by Cubelelo.