Defense class is taught by Sir Godric Gryffindor, and it teaches the basics of physical defenses and wizardry defenses.
Sword-play is common with the age, and is a vital skill to have. Students in this class, will learn fight with a broad-sword.
Not everyone knows how to throw a punch without breaking a wrist or knuckle. Let Sir Godric teach you to bust heads without busting hands.
Different types of charm to block anything from jinxes to minor curses. Sir Godric will teach you to protect yourself with these charms. Includes expecto patronum.
For almost every curse, there is a counter-curse. While being able to curse someone is a great skill, it does no good if the opponent is faster, so counter-curses are necessary.