Neat rock. Those look like secondary sedimentary structures formed by mineral precipitation in a fracture which have been subsequently smoothed by water tumbling. Some people call them ‘Liesegang’ bands but, strictly speaking, this refers only to structures with a concentric ring-like appearance although they all form in a similar way. Differential erosion can give them a 'relief' pattern where the lines and rings stand proud of the matrix. They’re relatively common features in sedimentary rocks, especially sandstone which is rich in iron oxides (but not exclusively so). When found in large exposures, it’s sometimes called ‘carpet rock’.
Here’s an example of Liesagangs in sandstone where the ring structures are constrained by those in linear fractures. You won’t always find both types together.
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[pic from Richard Childs’ ‘onlandscape.co.uk’]