What do "KeyPoint" contain when used with 2D feature detectors

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Hello all,

I was playing around with 2D feature detection algorithms, like AKAZE, ORB, SIFT and SURF.

After a little bit I wanted to see the coordinates of the features found. But when I saw the "KeyPoint" in which the features where saved, I saw that they are float. Of course this is logical (if we look here). But on the other hand, the Mat (that had the original image) has integer numbers to represent the coordinates of each pixel.

My question is, what do these Float numbers mean?? When "KeyPoint.pt.x == 2.5" does this mean the centre of the point is in between pixel 2 and 3?

Hope I was able to express it correctly.