Unattached ribosomes, also known as free ribosomes, are described by Seattlepi as intracellular bodies that initiate protein synthesis by translating messenger RNA. These bodies float freely in the cytosol. The mRNA that is translated by the unattached ribosomes stays in the cytosol.
Seattlepi explains there is a second type of ribosomes, which are called attached ribosomes. They are found on the outside of the endoplasmic reticulum and create a rough surface. They are also responsible for generating proteins, and as the National Center for Biotechnology Information explains, only the proteins generated by attached ribosomes can move outside of the cell.