A cell is the basic unit of living organisms that is capable of reproducing itself exactly. That is, although eukaryotic cells (such as plant cells and animal cells) contain components, which are called organelles, those components do not reproduce themselves independently of the cell of which they are a part.
Ribosomes are particles consisting of ribonucleic acid (RNA) and protein that interpret cellular information from the nucleus of the cell and synthesize appropriate proteins as required by the cell.
Ribosomes are either attached to the endoplasmic reticulum (specifically to the rough endoplasmic reticulum, RER) or free in the cytoplasm as polysomes.
See also the functions of cell organelles.