"No USB port , could you explain that for me ?"

A USB port is, essentially, a sort of socket which you use for attaching other devices to your tablet. For example, memory sticks can be plugged into USB ports and used for storing files on. In addition, you can buy wireless keyboards and mice - but they come with little WiFi 'dongles' which you need to plug into a USB port. Digital cameras can also, theoretically, be attached via a USB port - although photo files might be a bit big for a tablet. Lots of devices and gadgets come with USB connectors, these days, but you need a port to plug them into.