It's an acronym popularized by publishing company [O'Reilly] to designate one of the most popular [open-source] development stacks: [Linux] + [Apache] + [MySQL] + [PHP] | [Perl] | [Python]

Of course: it could well be "LAPT": [Linux] + [Apache] + [PostgreSQL] + [Tcl].  But i think it's missing a "S" in the beginning to make it work... :)