It's not some obscure symbol; it's just division. It just so happens that we typically "divide" matrices from the left when solving equations like this (and matrix "division" isn't commutative) so instead of `a/b` it's `b\a`.

Yes I know. It’s a solve operator…it’s equivalent to division only in the infinite precision world.

The \ operator differs from the / operator in that it doesn’t compute an inverse … it solves the system of equations. Solver algorithms are more numerically stable ( in that you’re much less likely to have large errors due to wacky input data).

Yes, I know. :)

I'd just say that solving the system of equations is the best way to divide by a matrix — that's why I put air quotes around "divide" above. In Julia, right-dividing matrices (with `A/B`) actually does the smart adjoint-commuting thing to left-divide it and do the solve (with `(B'\A')'`).