Paint thinners are solvents used to dilute or thin oil-based paints, varnishes, and other coatings. They help improve the flow and application of the paint, making it easier to work with. Common types of paint thinners include mineral spirits, turpentine, and acetone, each with specific properties and uses. In addition to thinning paint, paint thinners are also effective for cleaning brushes, tools, and surfaces that have been contaminated with paint. However, they can be hazardous if inhaled or ingested, so it's important to use them in well-ventilated areas and follow safety guidelines.