My son has a white thing on his gums and he wants to know what it is?

Lichen plan, leukopl: you may suffer from lichen planus, an autoimmune condition, or from leukoplakia, a prolonged irritation of tissue possibly due to smoking, drinking which gives rise to epithelial change( acanthoma)

Not enough info: Your question doesn't contain enough information to make a diagnosis. There are numerous "white things" that can develope on the oral tissues. Depending on your sons age please bring him to a pediatric dentist or a general dentist for an evaluation. Many white lesions are not a problem but an evaluation is the only way to be sure.

Contact DDS: See dentist for a differential diagnosis. What is the age of your son? Many variables including nothing, see dentist to alleviate your concerns for a clinical evaluation.

Please see Dentist: There are hundreds of things that cause white spot lessons in the mouth. Most are benign. Many are self limiting. Some are quite dangerous. Please ask your Dentist, an Oral Medicine specialist, or a specialist Oral Surgeon.