The medical condition lateral epicondylitis is more commonly referred to as "tennis elbow." Pain on the outside of the elbow is a symptom of a disorder brought on by overuse of the arm, forearm, and hand muscles. You don't have to play tennis to understand this, but it can be a serious issue for some tennis players, which is why the word was coined.
Tennis elbow is brought on by a sudden or gradual injury to the muscles and tendons on the outside of the elbow. Tennis elbow is a condition that affects the region where the tendons and muscles of the forearm join the elbow's lateral epicondyle, which is its outside bony portion. Lateral epicondylitis is what your doctor may refer to as. "Golfer's elbow" is another commonly used term.