Qt - 'Shadow Building'?

Additional information for Mateen's answer.

By default, Qt Creator builds projects in a separate directory from the source directory, as shadow builds. This keeps the files generated for each build and run kit separate. If you only build and run with a single kit, you can deselect the Shadow build checkbox.

https://doc.qt.io/qtcreator/creator-build-settings.html#qmake-build-configuration

Shadow building is a technique used to build different Qt builds of the same version for different platforms/compilers/etc. Your compiled build is in a different directory, separate from the original Qt source directory.

I've created a shadow build for my MSVS2010 compiler. If I wanted to, I could create a new build for MinGW in a different build directory.

See the definition here, and more information about configuring your build here.