Day-trading is any trading style that demands closing the position before the end of the day’s trading session. Its the hardest way to succeed in trading, though new traders often see it as low risk because you don’t hold overnight or over weekends, periods during which they cannot react to changing prices.
If they are relying on a changing chart set-up to drive their open trade management decisions (exit, enlarge or reduce), then they are right in theory. But in practice this does not work, as the TA permutations are too complex, fast and - even worse - transient, for this to work. 90% of traders who started trading in the last 3 months will be broke within the next 3. I bet that 90% of them only think of trading as day-trading. If you do what the 90% does in the same way they do it, you will probably get the same result.
Longer-term trading is much lower risk and uses much more reliable TA set-ups. There is more time to do TA and plan a strategy, more time and data is available to review and improve the strategy, element by element. Many day-traders don’t have a strategy as such, they simply decide they will be buying whatever because its price is higher than it was yesterday and has been rising for an hour today: or they will sell - for exactly the same reason - price is higher than yesterday and is higher than an hour ago. That’s not a strategy.