[tangentspace]

Of the parallelepiped generated by the columns of the matrix. (https://textbooks.math.gatech.edu/ila/determinants-volumes.h...)

The result of the determinant might be negative, which doesn't make sense for a volume, so you need to take the absolute value to interpret it that way.

Another way to think of it is the change in volume caused by the linear transformation determined by the matrix (http://algebra.math.ust.hk/determinant/01_geometry/lecture3....)