Linear polarization means that all the waves that arrive at a given point have their electric fields aligned in one plane. A single wave (photon) is always plane polarized. A circularly polarized wave has the electric vector rotating (either clockwise or anti) if you look along the direction of propagation.
Now sitting at the detector (antenna) site and looking at the direction of the approaching wave, you will see either the electric vector in one plane (plane polarized), randomly distributed (unpolarized) or rotating (circularly polarized). Now your antenna (detector of the electric field) can sense the electric field if it is so oriented (for a dipole antenna can detect a plane polarised wave). If the electric field is at an angle, only the component of the electric field onto the antenna is detected.