Nootropics are a class of drugs that improve mental functions such as cognition, memory (both long term and short), i.q., motivation, and concentration. Nootropics are thought to work by altering the availability of the brains supply of neurochemicals (neurotransmitters, enzymes, and hormones/neuro-steroids), by improving the brain's oxygen supply, by stimulating nerve growth, and inducing a phenomenon known as neurogenesis where new brain cells and neurons are formed in an already healthy brain.
One rather famous example is a drug called piracetam. First discovered in 1964 by a belgian pharmaceutical company, it has been approved by the FDA and doctors for treatment aging, alcoholism, neurodegenerative diseases like alzheimer's and age related dementia, as well as stroke and breath holding spells. There is debate about its role in treating symptoms of schizophrenia as no relief of symptoms are experienced but cognitive performance is increased.
Dosages are generally taken in an 800mg capsule taken 2-3 times a day with no serious side effects reported. It can cause a state of exictability characterized by insomnia, irritability, and headaches. These headaches are a result of piracetam depleting choline levels in your brain so supplemental choline intake with lecithin is advised.
Many college and university students report great success with piracetam as well as people involved with legitimate medical reasons.