more newbie questions

[rpjday <rpjday mindspring com>]

  ok, i got my repeating column fields to work, now a couple more
newbie questions.

1) can someone explain the distinction between absolute and relative
  cell references?  i've built a couple handy spreadsheets using
  references like A3, B12 and so on, which work just the way i would
  expect.  so what means $A2, A$2, $A$2??  where would one use these?

2) one spreadsheet i designed is for calculating invoices when i come
  back from a contract -- income, expenses, etc.  the usual stuff.
  right now, i have each invoice in a separate gnumeric XML file.
  is there a way to have a "book" of these invoices?  rather than
  keeping each one in a separate file?  each "page" (if you can call
  it that) would have to start again at A1 and so on.  is this
  possible?

3) most importantly, is this the right forum for newbie questions?
  i don't want to be wasting peoples' time.  thanks muchly.

rday