The polarity of an antenna is the orientation of the electric field of the radio wave with respect to the Earth's surface.

Antennas can have vertical polarization, horizontal polarization or both.

Polarization refers to the orientation of the electric field component of an electromagnetic wave with respect to the Earth’s surface.

An electromagnetic wave is composed of electric and magnetic fields propagating perpendicular to each other. Radio and light are both electromagnetic waves. 

Electromagnetic waves can propagate with linear, circular or elliptical polarization.

Linear polarization is the most popular method used in WiFi communications and can take two forms, vertical and horizontal.

Some antennas utilize dual polarity which provides access and interoperability with both vertical and horizontal polarized antennas.