"newbie" ?? about steppers, servos

As it states, I am just getting started learning about cnc,
home/hobby versions. Where can I get a book, etc. that explains
in "plain" English, the difference between a servo/stepper/encoders
with explanation on when each would be applicable. I know I can buy
everything one needs to build cnc machine/or conversions, etc., but
I haven't a clue what to buy. On one hand ,I do not want to but
something that isn't the right thing for the application,Yet I don't
want to buy something that is "overkill" either. Anyway, this ?? has
probably been asked before, but please point in me in the right
direction. Thanks, Tom in Ga.