ribosomes can be thought of as platforms on which proteins are synthesized. They are not merely a passive platform but play an active role in protein synthesis. The nature of this role is beyond the scope of this course.
Ribosomes can be dissociated into large and small subunits. Each is composed of proteins and RNA called ribosomal RNA (rRNA). As the diagram below indicates the each subunit is composed of different proteins and different RNAs.