Why Polarization describes the orientation of the electric field (and the magnetic field perpendicular to it). In a circularly polarized wave, the E and H field vectors rotate steadily about the direction of travel, completing one full turn each RF cycle, so the tip of the field vector traces a helix through space. This is produced by combining two linearly polarized components of equal amplitude that are 90 degrees out of phase, as with crossed dipoles fed in quadrature or a helical antenna. Circular polarization comes in right-hand and left-hand senses and is popular for satellite and EME work because it tolerates the unknown or shifting orientation of the far end, including Faraday rotation.
Watch out The idea of a field "bent into a circular shape" misreads the name: nothing about the wave is curved, it is the direction the field vector points that rotates. An ordinary loop antenna radiates linear polarization, not circular.
Circular = rotating, not curved. Two linear waves 90 degrees apart in phase make the field spin like a corkscrew.