A stock symbol is the shortened way of referring to a specific stock. It is sometimes called a ticker symbol or stock ticker symbol. 

Each stock has its own unique symbol that investors can use to ensure that their trade is placed accurately.

Another way to think of them is unique nicknames or usernames for stocks. They’re usually between 1 to 5 characters long but can be longer. A ticker symbol can refer to stocks, ETFs, mutual funds and other securities.