There are a few meanings. If you haven't heard it before, I am guessing you hear it in a context like "the LAMP stack." Basically, web applications are complex systems these days, and they rely on moving parts on top of moving parts. Stack describes that collection of programs/technologies.<p>For example, Bingo Card Creator uses a fairly typical Rails stack: application code in Rails(a web framework based on the language Ruby), MySQL for the DB, Nginx proxying to mongrel for the web tier, memcached and Redis for for a few purposes, DelayedJob for queuing, all running on Ubuntu.
You could find one answer here: <a href="http://en.wikipedia.org/wiki/Stack_(data_structure)" rel="nofollow">http://en.wikipedia.org/wiki/Stack_(data_structure)</a><p>In short: a data structure where the last thing you put in is the first you get out.<p>To others it means everything you can pile up in one or the other way. Like MySql on Linux with Apache and PHP which gives us the LAMP stack ...<p>To some weird people it might mean this: <a href="http://www.rocktownhall.com/blogs/media/blogs/rth/MarshallStack.jpg" rel="nofollow">http://www.rocktownhall.com/blogs/media/blogs/rth/MarshallSt...</a>