Different types of medicines are available to treat many different diseases. Some medicines only treat the symptoms and others cure the disease by killing the pathogens.
Painkillers are chemicals that relieve the symptoms but do not kill the pathogens. Common examples include paracetamol and aspirin, and they can relieve a headache or a sore throat.
As the symptoms are treated, your immune system still needs to combat the pathogen.
Antibiotics are substances that slow down or stop the growth of bacteria. They are commonly prescribed medicines, examples include penicillin and amoxicillin. These can be taken to cure the disease by killing the pathogen, but only cure bacterial diseases and not viral ones.
Antibiotics damage the bacterial cells but do not damage the host cells. They have the ability to cure some bacterial diseases that would have previously killed many people. Since their introduction, they have had a large influence on the world's health and death rate.
Different bacteria cause different diseases. One antibiotic may only work against one type of bacteria, or a few types. This means that a range of different antibiotics is needed for the treatment of the whole range of bacterial diseases.
Viral diseases cannot be cured by antibiotics, as they reproduce inside the host cells. It is very difficult to develop antiviral drugs, as they might damage the host cell whist killing the virus. Antiviral drugs only slow down viral development, and viruses change their antigens quickly which means new drugs have to be generated regularly.