What is the difference between blacking out and passing out? what are there dangers?

No difference: The terms "blacking out" and "passing out" are usually used to mean the same thing, (i.e. a person loses consciousness). An exception to this might be when these terms are used to describe what can happen when a person drinks too much alcohol. It is not uncommon for people to "pass out" when they drink too much. Some people may also "black out", they keep functioning but cannot remember it.

They are synonyms: These words are used interchangeably to describe symptoms of fainting or syncope. Blacking out--"all of sudden everything went black"--is usually the result of a heart rhythm problem. Passing out can happen more gradually--just crumbling to the floor or collapsing from low blood sugar, a seizure, the sight of blood, etc. Whatever the cause, it needs evaluation.

Same: If you meant losing consciousness, the implication would be the same. The dangers include hurting yourself or hurting others (as in passing out when driving). It may also signal something more serious. See doctor about this.

Interchangeable: Black out - stop remembering what happened Pass out - fall asleep/go unconscious The cause of the experience may actually determine the proper designation

Interchangeable: The terms can be interchangeable and either needs to be evaluated and the reason for such would need to be diagnosed as it could lead to serious medical issues. For example cardiac arrythmias, Blood pressure issues, anemias, seizure disorders, metabolic disorders, etc. etc. can all be possible causes.