pushd is one of the Tclx extended tcl commands. It is used to push the current directory onto a directory stack that can be used with cd. This permits one to keep track of a series of directories one has visited, and then do a popd to get directories off of the stack.
KPV I've never found pushd to be very useful on DOS/Windows because of file volumes and how each volume has it's own current directory. Using pushd has the unwanted side-affect of likely changing the current directory of the volume you're changing to. For example, if the current directory on volume F: is say "f:\myDirectory" and I call pushd f:\temp then popd and sometime later go back to that volume via f:, I'll be put into the directory "\temp" rather than "\myDirectory".
In fact, when I do need pushd's functionality, I end up needing to call it twice: once to get to the right volume, then to get to the right directory (and don't forget you'll need to call popd twice).
Also see "pushdpopd.tcl".