The prescription" is represent by a symbol "Rx". Rx is a transliteration of a symbol. There are various theories as to the origin of this symbol but in literal terms, "Rx" indicates an instruction "to take" what is specified in the prescription.
What is unique for each prescription is the name of the patient, date, the details of the medication and the directions for taking them. The prescription should be appropriately signed by the physician prescribing it.
Prescriptions are typically handwritten on preprinted prescription forms, or may alternatively be using computer these days. The prescription should contain the name and address of the prescribing doctor and any other legal requirement such as registration number of the physician.