FIR Filter Type - MATLAB
The filter order equals the number of taps minus $1$. The filter order is the order of the polynomial corresponding to the filter's transfer function. E.g.,

$$H(z)=h[0]+h[1]z^{-1}+h[2]z^{-2}\tag{1}$$

has $3$ coefficients (taps) but it is a second order polynomial (in $z^{-1}$), so the filter order equals $2$ (i.e., it has $2$ zeros and $2$ poles).

For type I and type III linear phase FIR filters, the filter order is even, i.e., they have an odd number of taps, whereas types II and IV have an odd filter order (even number of taps).