The reason that this can be confusing is because it used to be a generalization of all ailments of the lower leg. To narrow it down a bit this term refers to pain along the tibia which is the bone that is commonly called the shin in the lower leg. These are commonly called medial shin splints.
Many people experience pain that gets worse with the activity and is lessened by rest.
The activities that are the most aggravating are running, jumping, climbing up an incline, or running down a hill. Hard surfaces such as concrete aggravate the condition the most. The discomfort can range from tolerable, to pain so intense that it causes a limp. They are not used to running yet and they tend to overdo it. They are also not used to warming up properly then adding appropriate stretching.