Define virus and virion, and describe the parts of a virion.

A virus is a tiny infectious biological agent that can only replicate or duplicate inside the host cell. These infectious agents can infect all different types of living organisms ranging from animals and plants to microorganisms and archaea and bacteria.

Virions are ineffective particle or form of the virus outside of the host cell, with RNA or DNA and a protein capsid.

The main role of these infectious agent virions is to transfer the DNA or RNA genome from itself to the cell of host and expressed the gene which means produce proteins from the genome transferred to the host cell.