This may be a dumb question but what does splicing syntax give?

Or maybe I'm confused because these two paragraphs in the rationale
should be "splicing" instead of "non-splicing"?

"The usefulness of the non-splicing versions seems to be
non-controversional. For example, SRFI 148's em syntax would become
unnecessary.

Thus, this SRFI proposes the non-splicing versions of let-syntax and
letrec-syntax for R7RS under a different name."
--
Duy