What's the difference between gel, liquid, and tank highlighters?

Gel highlighters are dry crayon-style sticks that resist bleed and smearing, ideal for thin paper. Liquid highlighters use a flowing ink for vivid, even color but can bleed. Tank (traditional) highlighters hold ink in a reservoir with a chisel tip and offer bright neon coverage at low cost. Each has a place depending on paper weight and whether you prioritize vibrance or no-bleed performance.