A ribosome is one of the several cellular organelles. Ribosomes are involved in protein synthesis, which is a very important function. You can find more information here: http://biology.clc.uc.edu/courses/bio104...

Ribosomes are large complex RNA and protein molecules that are composed of approximately 50 proteins and long strands of rRNA. These are the sites of protein synthesis and are called protein factories of the cell.