Hi Mattoo.
Polarisation refers to the electric field so that if the antenna is horizontal so is the polarisation.
Vertcal is vertical.Keeps it simple that way .The magnetic part of the field is opposite.
If they are referring to a hori antenna polarised vertically they must be on drugs or referring to the mag field for some obtuse reason to confuse you.
In a practical sense verticals speak to verticals more efficiently, same for horis and hori's work better together.
Over long distances this can be a moving feast but line of sight the above generally applies.