Virus and virion are two forms of microscopic, obligatory parasites. There are several differences between the two. 

Virus

A virus is a microscopic, non-cellular structure that consists of a nucleic acid molecule covered by a protein coat. It is an intracellular parasite.

A virus is relatively larger than a virion and may have different shapes. It may be helical, prolate, or icosahedral among others. 

Virion 

Virion is the active, infectious form of a virus outside the host cell. It has both nucleic acid as well as protein layers and is an extracellular parasite.

Virion is relatively smaller than the virus and is generally spheroidal in shape. Virions of most plant viruses are rod-shaped.