The different types of rehab facilities fall into two categories or “settings.” The two settings are inpatient (full-time rehab) and outpatient (part-time rehab). Inpatient means the client lives at the facility, and each step of the rehab process is typically completed there. Patients who attend an outpatient facility return home after treatment each day and often complete the steps of rehab at different facilities. Below is a comparison of the most common program options within those two rehab settings.
Certain drugs (like cocaine, heroin, and methamphetamines) are infamous for how they can mess up the brain. Most people know to beware of their potency and danger. Other substances (such as alcohol, marijuana and painkillers) tend to be viewed quite differently. For many Americans, they are deemed to be much less dangerous. But is this view accurate?

Nalmefene, an opiate antagonist that is similar in its chemical structure to naltrexone, is one of the most recent drugs being investigated for the treatment of alcoholism. Like naltrexone (sold as ReVia, Depade, or Vivitrol), nalmefene deprives the person struggling with substance use of the pleasurable feelings associated with drinking. But nalmefene is less toxic to the liver than naltrexone. As of 2013, nalmefene was still undergoing clinical trials through the U.S. National Institutes of Health before receiving FDA approval. From Rehab to a Body Bag | Dying for Treatment: VICE Reports (Full Length)

The first step in treatment is brief intervention. The physician states unequivocally that the patient has a problem with alcohol and emphasizes that this determination stems from the consequences of alcohol in that patient's life, not from the quantity of alcohol consumed. Emphasizing the effects on family, friends, and occupation, as well as any physical manifestations, is important. Pointing out that loss of control and compulsive use indicate alcohol dependence also is important.
Insurance: Many types of insurance cover the cost of addiction treatment and rehab; in particular, the Affordable Care Act requires that insurance policies issued under the state health exchanges and through Medicaid programs under the ACA expansion must provide coverage for addiction treatment. It’s important to note that insurance coverage often still requires that the individual provide a co-insurance payment, and some require a deductible be paid before treatment will be free. Specific plans may have different coverage levels, so it’s a good idea to check the specific policy or talk to the insurance provider. What happens in rehab?

Usually, however, drug classification under such legislation is not related simply to addictiveness. The substances covered often have very different addictive properties. Some are highly prone to cause physical dependency, while others rarely cause any form of compulsive need whatsoever. Also, under legislation specifically about drugs, alcohol and nicotine are not usually included.[46]

^ Nestler EJ (August 2016). "Reflections on: "A general role for adaptations in G-Proteins and the cyclic AMP system in mediating the chronic actions of morphine and cocaine on neuronal function"". Brain Research. 1645: 71–4. doi:10.1016/j.brainres.2015.12.039. PMC 4927417. PMID 26740398. These findings led us to hypothesize that a concerted upregulation of the cAMP pathway is a general mechanism of opiate tolerance and dependence. ... We thus extended our hypothesis to suggest that, particularly within brain reward regions such as NAc, cAMP pathway upregulation represents a common mechanism of reward tolerance and dependence shared by several classes of drugs of abuse. Research since that time, by many laboratories, has provided substantial support for these hypotheses. Specifically, opiates in several CNS regions including NAc, and cocaine more selectively in NAc induce expression of certain adenylyl cyclase isoforms and PKA subunits via the transcription factor, CREB, and these transcriptional adaptations serve a homeostatic function to oppose drug action. In certain brain regions, such as locus coeruleus, these adaptations mediate aspects of physical opiate dependence and withdrawal, whereas in NAc they mediate reward tolerance and dependence that drives increased drug self-administration.
The specific medicines prescribed will vary depending upon your own particular experience of withdrawal and the symptoms you are manifesting, and it may be that certain medications will not be appropriate depending on your substance of abuse or your own personal health history; an experienced medical professional will be able to make those decisions to ensure you go through withdrawal as safely as possible. What happens in rehab?