Usually refers to applications from the Sysinternals Suite (eg. Process Explorer, Process Monitor, RAMMap, ...)

The Sysinternals web site was created in 1996 by Mark Russinovich and Bryce Cogswell to host their advanced system utilities and technical information. Whether you’re an IT Pro or a developer, you’ll find Sysinternals utilities to help you manage, troubleshoot and diagnose your Windows systems and applications.
Sysinternals Suite
The Sysinternals Suite is a suite of applications for administrators to better manage their Windows Systems.
Notable applications include:
- Process Explorer - A Task Manager replacement
- Process Monitor - An application monitoring tool
- PsExec - Allows to (remotely) execute applications
- RAMMap - Gives an overview of how your RAM is currently used.