Trading bots exist and also functions! However, they function based on a user-defined strategy! If you see someone claiming that their trading bots are AI enabled and takes decision on your behalf, keep clear of them because such things don't exist! That's the reason why everyone is not winning the market!

In trading bot, you are basically using your own brain to take a position in the market, the bots just executes your own strategy! Bots themselves don't think or take decisions on your behalf!