Connect a USB slave into Arduino using FTDI Probably I'm asking a nonsense question but I'm new at interfaces.

I want to connect an USB barcode scanner to an Arduino (Uno or Mega). I've read that I need a USB host shield to achieve this. But I don't have any. I have a FTDI, so I suppose I could plug the USB output of the scanner into the FTDI and connect the FTDI to the UART port of Arduino. Then, I would be passing the USB output to Serial.

Is it correct? Thanks and sorry if I said something stupid!
No, that is completely wrong.

In USB you have hosts and devices. A device has to connect to a host. Your FT232 is a device. The barcode scanner is a device. Both of them need to be connected to a host for them to do anything.

So you need a USB host shield to act as that host.

However - check the manual for your barcode scanner: it may well have a RS-232 mode that it can be switched into (may need a different cable attached).