Copy trading is the automatic mirroring of trades from one account into another. When the source account buys, the copied account buys the same instrument at the same time, usually in the same size. Traders use it to run one strategy across several accounts, or to follow a strategy they did not build themselves.
Firms draw a sharp line on whose trades you may copy. Some plans expressly allow copying between your own accounts. Copying another trader's signals, or running the same strategy across accounts held by different people, is banned at many firms, because it looks like one trader operating several accounts to game the rules.
This matters because a ban breach ends the account, and the firm detects copying from order patterns, not from confessions. Two accounts placing identical trades within seconds of each other are easy to spot, even if the traders never speak.
The common trap is assuming that copying your own trades is the same as copying someone else's. Read the copy policy on the rules page and check whether it covers your own accounts only, signal services, or both. Prop trading can cost you every fee you pay.