1. Messenger RNA (mRNA): This type of RNA carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are made.

2. Ribosomal RNA (rRNA): This type of RNA is a key component of ribosomes, the cellular machinery that translates mRNA into proteins.

There are other types of RNA with important functions:

* Transfer RNA (tRNA): This RNA brings amino acids to the ribosome during protein synthesis, matching them to the codons on mRNA.

* Small nuclear RNA (snRNA): These RNA molecules are involved in splicing, the process of removing introns from pre-mRNA.

* Micro RNA (miRNA): These small RNA molecules regulate gene expression by binding to mRNA and inhibiting its translation.

So, while mRNA and rRNA are the most fundamental types, the variety of RNA molecules demonstrates their diverse and essential roles in cellular processes.