Sir, i've just passed the 10th examination and wanna crack the iit jee. Sir i've never understood the concept of a virtual image . What is it?

Well a virtual image is basically an image formed when light rays APPEAR to converge at a place , i.e they really do not meet there . It is not possible to catch a virtual image on screen . If it is a virtual image formed in the mirror for example , we can easily understand the fact that it can not be caught on screen.