Dear doctors, i would like to know. what is on the back my body. i have a light brown spots at the back of my body and under my arms. ?

Café au lait spot?: Café au lait is french for "coffee with milk" and refers to their light-brown color. I can't be sure what you have--just a guess. Having multiple--6 or more of greater than 5mm before puberty or greather than 15mm after puberty, is a one of diagnostic features of neurofibromatosis-1. These can also be associated with many other medical conditions. Fungal rashes can appear same, but often with "many spots." consult doc. Good luck.

Light Brown Spots: Light brown spots can be tinea versicolor which is a superficial yeast. Treatment is with oral or topical anti yeast medication. Visit your local dermatologist for a definitive diagnosis as i cannot see your skin.