Physiology studies physical, mechanical and biochemical functions of living organisms.  There are two branches of physiology: plant physiology and animal physiology.

Human physiology is the most complicated area in physiology.  The main focus of human physiology is the bodily organs and systems.  Considering Anatomy studies form and physiology studies function, anatomy and physiology are closely related. 

So you might know about anatomy, but what about physiology? It looks at things such as:

The nervous system which includes the central nervous system and peripheral nervous system.

The musculoskeletal system includes the human skeleton, which includes bones, ligaments, tendons, and cartilage and attached muscles.

The circulatory system includes the heart and blood vessels.

The gastrointestinal system includes the mouth, esophagus, stomach, gut (small and large intestines), and rectum, as well as the liver, pancreas, gallbladder, and salivary glands.

The respiratory system includes the nose, nasopharynx, trachea, and lungs.

The urinary system includes the kidneys, ureters, bladder, and urethra. 

The immune system includes the white blood cells, the thymus, lymph nodes and lymph channels, which are also part of the lymphatic system.

The endocrine system includes the principal endocrine glands: the pituitary, thyroid, adrenals, pancreas, parathyroids, and gonads, but nearly all organs and tissues produce specific endocrine hormones as well.

The reproductive system includes the gonads and the internal and external sex organs.

The integumentary system includes the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands.