The feeling of being "high" is a complex experience that can be caused by a variety of substances and their effects on the brain.

Here are some common examples:

* THC (tetrahydrocannabinol): This is the main psychoactive compound in marijuana. It binds to cannabinoid receptors in the brain, which are involved in mood, memory, and perception.

* Alcohol: Ethanol, the type of alcohol found in drinks, affects the brain's reward system and can lead to feelings of euphoria and relaxation.

* MDMA (ecstasy): This drug increases serotonin levels in the brain, leading to feelings of happiness, empathy, and energy.

* Amphetamines: These stimulants increase dopamine levels in the brain, leading to feelings of alertness, focus, and euphoria.

* Opioids: These drugs, like heroin and morphine, bind to opioid receptors in the brain, which are involved in pain perception and pleasure. This can lead to feelings of euphoria, relaxation, and pain relief.

It's important to note that each of these substances affects the brain differently, and the specific effects can vary depending on the individual, the dosage, and other factors.

Using drugs to achieve a "high" can have serious risks, including addiction, overdose, and long-term health problems. It's important to be aware of these risks and to make informed decisions about your health and well-being.