AMP files are so-called Adobe Arbitrary Map files, so own (arbitrary) curves of the image editing software Photoshop. Below this is a hand drawn curve in the Photoshop color curve dialog using pen mode, which influences the RGB color values (red, green, blue) and tone settings (saturation, brightness) of a loaded image.
The curve dialog box can be reached under 'Image-> Adjustments-> Gradation curves', in which you can load and save your own curves. The curves are called effect curves.
It should be noted that the pen is selected before saving, otherwise an acv file (gradation curve) will be generated.