What graphic card is Radeon tropo xt2 actually is? It has heen included in Lenovo Z51-70 Notebook (80K60021IN) as 4gb graphics

No, it is a little less powerful than a nVidia 940m. The 4GB of VRAM is basically a waste since GPUs like the 940m are too weak to play games at 1080p resolution and ultra settings. Though it would be helpful for people using Photoshop and a lot of filters.