All-time high (popular ATH) and all-time low (popular ATL), refer to the highest and lowest trading prices that a stock or other financial instrument has ever reached since it began trading. ATH is the highest price that a stock has ever traded at, while ATL is the lowest price that a stock has ever traded at. Investors may use the all-time high and low as a reference point for assessing the current price of a stock, and for making trading decisions.
It’s important to note that just like the all-time high and low, the 52-week high and low, are historical prices and do not necessarily indicate the future performance of a stock. The stock's current price and future prospects should be evaluated based on a variety of factors, including its financial performance, industry trends, and broader economic conditions.