Day trading is the act of buying and selling securities or financial instruments within the same day on the basis of short-term fluctuations of prices. You can sell these financial instruments many times within the day if you take advantage of small price moves in the market. Read more about day trading in this link here.
Day trading is different from investing. Investing is the act of buying stocks of an asset that will hopefully build profits over time. Investing is concerned with the business they invest in. Most brokers or individual investors look for companies that can make solid profits and a strong pipeline of products in the long run.