Copy trading automatically replicates another trader's (the "signal provider's") positions into a follower's own account, proportionally scaled to the follower's account size, without the follower needing to place any trades themselves. It's marketed as a way to benefit from an experienced trader's strategy passively, though the follower still bears the full risk of whatever losses the copied trader incurs.
Past performance shown on a copy-trading leaderboard is historical, not guaranteed, and a signal provider's risk-taking can change (often for the worse) once they're trading with followers' capital rather than just their own.
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Guide
Choosing a Trading Platform: MT4, MT5, cTrader and the Broker's Own
The platform decides which orders you can place, whether your stops survive a closed laptop, and how much you would have to rewrite to leave. What actually differs between the options — and the point where the platform stops mattering and the broker takes over.