'Illegal drugs' include heroin, cocaine, ecstasy, LSD and cannabis (these are divided into Class A, B or C depending on how addictive they are).
'Recreational drugs' are drugs that people use for pleasure or relaxation. Most recreational drugs are illegal. However, alcohol and tobacco are legal recreational drugs. (Some religious people would include caffeine as a 'recreational' drug and would avoid its use.)
'Prescription drugs' are those prescribed by a doctor to treat a medical condition, and are legal.
For more information on all types of drugs Ask Frank using the A-Z search list which will give you a breakdown of all the different types and names for drugs, their effects, the risks, what the laws says and much more.