Few questions about info program

I have a problem with some commands in info. 1. I found that C-x means not C but Ctrl. 2. In addition I have a problem with "M-x" (this is probably not "M" key (shift+m), and RET is the Enter key?? 3. There is also "LFD (select-reference-this-line)" and I have no idea which key is that.