The 52 week high is the price that a stock has been traded at in the last 52 weeks, which is roughly one year. This is figured out by looking at the prices of the stock.
They look at all the prices of the stock for the past 52 weeks and find the highest price that the stock reached during that time.
Many traders watch the 52 Week High because they think it can be a sign that the stock's about to take off or keep going up.
Not always. A stock at its 52-week high may rise. Before buying 52 Week High stocks, research the company, its stock value, and your risk tolerance.