Usually, developers refer to "their stack" as the technologies they know to base their programs and systems on. This is also called a solution stack or tech stack.
A stack can also be a data type where you have a collection of objects which are processed programmatically. See Stack (abstract data type) on Wikipedia.
A "full stack developer" is a developer who knows every element of the software stack their application runs on. Usually this doesn't include the operating system, but very much the runtime environment, databases, storage systems and frontends.
| Acronym | Meaning | Description/Comment |
|---|---|---|
| JAM | JavaScript, API and Markup | Most of the stuff happens client side |
| LAMP | Linux, Apache, MySQL and PHP | nowadays it's usually MariaDB instead of MySQL |