Cloth masks are used as a barrier against large airborne droplets and to prevent you touching your face. The are also used to diminish the effects of air pollution. However, they are not a replacement of a proper medical masks. Each mask has a pocket to add a tissue, gauze or kitchen towel to provide extra protection. They are easily washable and should be washed in hot water and detergent after each use.
Due to shortages of surgical masks we are advised not to hoard masks, as they are required for medical staff and people who are unwell. In the absence of medical masks these cloth masks are the next best thing.
The best medical advice to prevent infection, is to wash your hands regularly and try to not touch your face.