What's is the Least significant File and Least Significant Rank? I'm Reading this tutorial and there are 2 definitions that confuse me :

https://chessprogramming.wikispaces.com/Square+Mapping+Considerations

What's is the Least significant File and Least Significant Rank ?
LSF and LSR are two ways to encode a chess board coordinate into a single integer number. LSF does that by { a1, b1, c1, ... } while LSR encodes by { a1, a2, a3 ... }.