A very fundamental concept in Scheme is quoting. Unfortunately it is often made unnecessarily confusing for new users. If introduced slowly enough and digested thoroughly the idea isn't that complicated after all. But instead users are mostly confronted with it through code pasted from some helpful snippet, and when trying to modify that unknown code they are left alone with sloppily placed comments on mailing lists or ready-made corrections.
Quoting is hidden beneath the keywords
unquote-splicing and their slightly confusing shorthands
' (single quote),
, (comma) and
@ (at), combined with picky requirements regarding the placement of parens.
Being thrown back to one's own experimentation and to trying to adapt other's code is a recipe for frustration in this case. Therefore we'll proceed slowly and dissect this valuable item in the Schemer's toolkit step by step.