The term alcohol is referring to the primary alcohol that is called ethanol or also called ethyl alcohol. It is used as a drug, it can be addictive, and it is the main alcohol present that we can find in alcoholic beverages.
Depressant has a meaning of drug that can lower neurotransmission levels.
Intoxication is also called poisoning which is caused especially by alcoholic drinks or also narcotics.
These three terms are connected because alcohol is classified as a depressant of the central nervous system and people can get intoxicated by it.