A 212(h) waiver is used for people who have criminal convictions and are inadmissible to the United States.
You have to demonstrate that their denial into the United States would be an extreme hardship to a U.S. citizen or legal resident that is a parent, child, or spouse.
A 212(h) can be done with a Green Card application.
If you have never been in removal proceedings, have a criminal conviction, and are eligible for a Green Card, you can apply for a green card with a 212(h) waiver. If the 212(h) waiver is denied by immigration, you could be placed into removal proceedings.
A 212(h) waiver will waive your ground of inadmissibility for criminal activity, if it can.
You rarely can waive drugs under a 212(h) waiver. If you do not have a Green Card and you have been convicted of a drug offense, other than 30 grams of marijuana, you will never be eligible for a Green Card based on family or employment.