Oregon Spark Tester

The inline Oregon Spark Tester 42-087 has a clip for grounding, and an uninsulated terminal that hooks up to spark plug wire. Is the other terminal, that sits at about a 45 degree angle and except for the end, is covered by a black insulating material, a ground also? If it is, the spark does not have to jump very far. Also, if wanting to see the spark jump the wide gap, seems to me that one has to be careful that the bare end of the 45 degree terminal does not touch ground. Question is, why is it even there?