Here is probably the most common Lampholder used in this country.  The John Smith of the Lampholder world, it simply hangs on the end of a wire in the centre of a room. It has a simple cordgrip mechanism to stop it coming off the cable.  The skirt unscrews so a shade can be attached.  It has a metal insert and takes up to 100 watts.

Before starting any electrical work, always switch off at the mains.  If in doubt consult a competent electrician