Hi,
The 'pole' is polarization.
So, one electromagnetic wave can be characterized by her polarization of the electrical field (E-field) :
in the orthogonal plane of propagation, the E-field can be moving in several ways.
If the E-field describes one ellipse : the polarization is elliptical
If the E-field describes one circle (heliax in reality, versus of time) : the polarization is circular left-hand or right hand.
If the E-field describes one straight line : the polarization is linear.
https://en.wikipedia.org/wiki/Polarization_(waves)
But the polarization wave of any antenna is not perfectly.
Example, one antenna that works in left-hand polarization (co-polarization) has one component, the 'cross polarization' (much smaller) of right-hand polarization.
This cross-polarization is radiated like the co-polarization and can be observed through the patterns radiation.
Look on courses or the web the link between 'AXIAL RATIO' and 'CO/CROSS POLARIZATION'.
BR