A ticker symbol is used to identify publicly-traded companies. These can be a combination of letters and numbers. Usually you will see these as 1-5 letters.
A company's ticker symbol can be useful in identifying the company you are researching. For example, if you do not know the exact company name or spelling or if more than one company has a similar name, the unique ticker symbol can help.
Where do you find ticker symbols? There are a variety of easy-to-locate resources that provide this. Google Finance is a good choice. Just type a company name in their search box, and they will give you a list of choices.