The 4 categories of medication are General Sales List (GSL), Controlled Drugs, Pharmacy Medicines and Prescription Only Medicines (POM). They each have different marks to help identify them:
General Sales List (GSL) - These can be brought almost anywhere. GSLs include paracetamol, vitamin supplements and cold and flu remedies.
Controlled Drugs - The packaging is marked with 'POM' and 'CD'. These are the most serious category of drugs so they require a prescription from a medical professional.
Pharmacy Medicines - The packaging is marked with 'P' and are only available to buy at a pharmacy.
Prescription Only Medicines (POM) - The packaging is marked with 'POM'. POM medicines are similar to controlled drugs where they have to be prescribed by a medical professional e.g. anti-depressants or insulin.