What is lupus? So confused by all the lupus terms.

Autoimmune disease. Lupus erythematosus is a chronic inflammatory disease of unknown cause. The immune system attacks the patient's own body (autoimmunity) and can inflame the skin, joints, kidneys, nervous system, lungs, mucous membranes, and other internal organs. A red rash is often but not always present hence the term lupus erythematosus meaning "red wolf.".
Systemic autoimmune. It is a systemic autoimmune syndrome. Autoimmune because the immune system attacks the persons own self by immune processes. Immune processes are usually felt to defend the body, but in this case the attack is against self thus auto or self immune attack rather than use the immune system to protect the person.