Axial vector and pseudo-vector seem to mean the same thing, and are dual to bivectors.
A bivector is a "directed area". (similar to how a vector is a "directed length") In three dimensions, a directed area can be represented by its normal vector (i.e. it's "axis"): that's where pseudovectors come from.
Similarly, in three dimensions, a "directed volume" can be represented by a number: that's where pseudoscalars come from.