Is there a difference between Image Alignment and Stereo Rectification for stereo correspondence or matching? As far as I know,
Image alignment just finds the best fit given two images of the same scene.

Whereas Image rectification, with regards to stereo vision, warps the images so that the epipolar lines are all on the same level. Essentially all common pixels between the two images are warped to be on the same y axis.

My question is, what is the difference between Image Alignment and Image Rectification, given a pair of images, when doing stereo correspondence?

If I were to find the disparity between two images, how is image alignment different to image rectification?
There two ways to look at this problem.

In simple terms, image rectification warps both images onto a common coordinate frame by typically estimating the transformation using the epipolar geometry.
Image alignment finds the transformation from one image to the other. It doesn't guarantee any constrains on the epipolar geometry and only one single image is warped.

Image rectification might benefit from image alignment (of local patches) to obtain the correspondences. Once these are found, the epipolar lines can be forced to be parallel.