Day trading means opening and closing a position within the same trading session — a day trader typically holds nothing overnight, closing every position before the market closes. The goal is to capture short-term price movement within a single day rather than holding through a longer trend.
It's distinct from swing trading (holding for days to weeks) and long-term investing (holding for months to years) mainly by timeframe, but the practical differences are larger than that: day trading requires watching the market actively during the session, generates far more individual trades and therefore more transaction costs, and is generally considered higher-risk given how much can happen — and how fast — in a single session.
In the United States, frequent day trading in a margin account can trigger "pattern day trader" rules with their own minimum equity requirements — a regulatory detail specific to real brokerage accounts that a simulated account like WOWS's paper trading doesn't need to enforce.