Hi all, I am new to General Relativity and I started with General Relativity Course on Youtube posted by Stanford (Leonard Susskind's lectures on GR). So first thing to understand is transformation of covariant and contravariant vectors. Before I can understand a transformation, I would like to know how do they look like. I mean what is the difference between covariant and contravariant vectors? And what is their role in understanding GR? In addition, I would like to know what is the application of Einstein's Field Equations? I mean, can I get one problem where they are actually used? Thanks! Joe W.