Update doc/manual/source/glossary.md

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

Author: edolstra

doc/manual/source/glossary.md

@@ -35,7 +35,7 @@
 
   A derivation can be thought of as a [pure function](https://en.wikipedia.org/wiki/Pure_function) that produces new files from existing files, taking into account how these files refer to each other.
 
-  In Nix, linked files are represented as [store objects][store object].
+  A derivation can be thought of as a [pure function](https://en.wikipedia.org/wiki/Pure_function) that produces new [store objects][store object] from existing store objects.
   Derivations are implemented as [operating system processes that run in a sandbox](@docroot@/store/building.md#builder-execution).
   This sandbox by default only allows reading from store objects specified as inputs, and only allows writing to designated [outputs][output] to be [captured as store objects](@docroot@/store/building.md#processing-outputs).
   How exactly to invoke such an isolated process is encoded in a [store derivation].