Welcome to another of the bees in my bonnet – the use of an external sound card while DJing from a laptop.
First question: what is an external sound card?
Very simply: it’s a gadget, usually USB-powered. You plug one end into your laptop. You plug the other into a mixing desk, some kind of speaker, headphones, you name it. Sound comes out.
Second question: I have a perfectly good headphone socket on my laptop – why on earth should I spend money on something like this?
Well – there’s a host of answers to this.