A 3D Ready television is compatible with 3D features such as the Blu-Ray 3D standard. 3D ready televisions also have a higher refresh rate, generally 120Hz and will also operate in 2D mode. Generally HDMI standard 1.4 is supported and are supplied with glasses which are told which eye should see the current image.
The televisions and glasses use stereoscopy techniques to rapidly show two sets of 2D images to each eye in turn which creates the 'illusion' of a full 3D image to the viewer. This is the reason for the higher refresh of 3D ready televisions.