Haram is what Allah has forbidden, for example, Pork, adultery, and so on.\nMakrooh is what is discouraged. For example, oral sex (yes, this is fact.) is makrooh because the human fluids are considered dirty and that's why you have to wash yourself (Ablution) before prayer to cleanse yourself if you have ingested, spilt, dispensed, any bodily fluids whether you have commited intercourse or not.\n\nThere has been some debate about smoking being haram or makrooh. My Saudi friend tells me it is actually haram, because what is addictive and harms your health is definately haram.