[linuxiran] Symbolic name

[Seyyed Mehdi Sheikhalishahi]

Hi All
What mean symbolic name in the following text?
* Unpack the binary distribution into a convenient location so that the
  distribution resides in its own directory (conventionally named
  "jakarta-tomcat-4.0").  For the purposes of the remainder of this document,
  the symbolic name "${catalina.home}" is used to refer to
the full
  pathname of the release directory.

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