The oil filter is constructed with a filter that allows oil to flow through it, but traps solid particles suspended in the oil. By capturing these impurities, the filter helps keep the oil clean and in good condition to lubricate and protect the engine's moving parts. It's important to take proper care of it, use quality filters, and perform visual inspections to detect problems. Always keep track of your oil changes; this is important to keep in mind when changing it. The oil filter is the shield that protects your engine from impurities.