The price movements of any stock are posted throughout the trading day and summarized at the end of the trading day. For example, April 2, 2019, shares of Apple Inc. (AAPL) opened at $191.09 and closed at $194.02. During the day, as indicated in the "day's range" listed to the right of the closing price, shares dropped as low as $191.05—the intraday low—and hit a peak of $194.46—the intraday high.
But this description of swing trading is a simplification. In reality, swing trading sits in the middle of the continuum between day trading to trend trading. A day trader will hold a stock anywhere from a few seconds to a few hours but never more than a day; a trend trader examines the long-term fundamental trends of a stock or index and may hold the stock for a few weeks or months. Swing traders hold a particular stock for a period of time, generally a few days to two or three weeks, which is between those extremes, and they will trade the stock on the basis of its intra-week or intra-month oscillations between optimism and pessimism.
In addition to knowledge of basic trading procedures, day traders need to keep up on the latest stock market news and events that affect stocks—the Fed's interest rate plans, the economic outlook, etc. So do your homework. Make a wish list of stocks you'd like to trade and keep yourself informed about the selected companies and general markets. Scan business news and visit reliable financial websites.