I have no idea about what a lot of this stuff means, I know what the scale names are and what not, but I don't understand the starting from different chords. What? How do I know which chord I would be starting on.. I was never aware that you could do scales only on certain chords, can someone tell me if this is true? AND, what are some good scales that I should learn if I want to get into lead and what not, like the core scales if there are any. Is there a guide to all of this that I can go look at?

Any help is appreciated.