In this basic UI there are only 2 important elements:

The Health Glow. This glow or bar is a representation of your percentage health. There should be a noticable 'full-health' status, but everything else is a smooth degradation until it goes black at death. It can also have an over-glow for a health level beyond 100%. Other effects could be coloration for states such as poison or stunned.
The Strike Orb. This shows the strength and affectivness of your attacks. The procedural lightning display is based on a formula taking into account the health of the enemy, the damage dealt, and the effectiveness of the blow. A simplified explaination could be the damage done as a percentage of remaining health. This should become more clear later.