A sore throat is caused by inflammation or infection of the throat and nearby areas. Strep throat is the most familiar cause of this, but other infections can cause it too. Your immune system is attacking something in the area and causing inflammation.
There are two main types of sore throats: viral and bacterial. Viruses like colds, flu, or chickenpox cause viral sore throats. Bacterial sore throats are caused by bacteria such as strep throat or staphylococcus. A bacterial sore throat can be serious if not treated immediately because it can lead to more serious health problems if left untreated for too long.