The two main types of RNA involved in protein synthesis are messenger RNA (mRNA) and transfer RNA (tRNA). mRNA serves as the template that carries genetic information from DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis occurs. tRNA, on the other hand, transports specific amino acids to the ribosome, where they are assembled into a polypeptide chain according to the sequence of codons on the mRNA strand. Together, these types of RNA play crucial roles in translating genetic code into functional proteins.