Can anyone explain ImageMagick or GraphicsMagick in TYPO3? I can't understand those tools.
I try hard to understand these tools
TYPO3 uses UmageMagick or GraphicsMagick to do image computation outside the limits for webcalls. A web call results in an execution of PHP with limited resources (time and memory). To avoid this restrictions TYPO3 does a shell call to IM/GM for computations on images.
Image computation is done mostly in form of resizing, but in general you could do many more with the GifBuilder.
Some examples can be seen in the InstallTool / AdminTool -> Environment -> Image Processing.
That's also the place where you check whether the configuration does work.