Image patches mean sub images. When an image is divided into disjoint or overlapping sub-parts, these sub-parts are called patches of that image. In image pre-processing, it is useful in feature extraction. For example, a 100X100 image can be divided into ten 10X10 patches.
In MATLAB, every digital image is considered as a matrix with defined maximum number of rows and columns. The 100X100 image is a matrix of 100 rows and 100 columns. When this matrix is divided into sub matrices, each sub matrix is termed as a patch of the original. The code for dividing a 100X100 image into the first 10X10 patch would be: