Cefaclor belongs to the class of antibiotics known as cephalosporin antibiotics. It works by stopping the growth of the bacteria. As it is an antibiotic, it is only effective against bacterial infections and cannot treat fungal or viral infections. 

Thus, it can be used to treat various bacterial infections in the body, including urinary tract infections, otitis media, skin, and soft tissue infections, upper and lower respiratory tract infections, etc.