There are three symbols in relativity textbooks that I've never encoutered before and need lots of help with. 1.Einstein summation convetion : Though not really a symbol i still don't quite understand what is meant by it. 2. Upper case lambda with super scripts and subscripts: It seems to be some sort of linear transformation, but I still don't quite understand it. 3. The great demon, the kronecker delta: I really cannot understand what is meant by this. The reason I have such a hard time with this notation is because I have very little formal education. However after the symbols are understood, it becomes very lucid. Can someone please give me a CLEAR and informal description of what this means with examples relating to relativity and tensor analysis? I'm very sorry.