A ticker symbol is usually an abbreviation as a designation of a listed company in the USA. This symbol consists of 1-4 letters depending on the nature of the stock market and importance of the company.
The letter F, for example, reserved for the Ford company. Basically represent all shortcuts with 1-3 characters the NYSE, while those are listed with 4 letters on the NASDAQ.
In Germany, however, the 6-digit security identification number (ISIN ) or more recently the ISIN is used.