The default DDNet theme is bright. If you play late at night, a "Dark" texture pack can turn that blinding white background into a soothing dark grey or black, saving your eyes from strain.
In the context of (Dyracuse’s D-Race Network), "Paper" refers to a specific community-made texture pack that replaces the default game assets with a simplified, minimalist aesthetic resembling paper or flat cutouts. Key Features of the Paper Texture Pack Ddnet Texture Packs