RNA stands for ribonucleic acid.
There are many different types of RNA, and two of the major types are those involved in the synthesis of proteins.
Messenger RNA (mRNA) is made in the transcription of DNA. It is almost a copy of a part of the DNA that will code for a protein that the cell wants to make.
mRNA can go out of the nucleus to the ribosomes. Ribosomes are protein producing factories. They read the mRNA code that tells the ribosome which order to put to the amino acids in to make a polypeptide. A polypeptide is a string of amino acids. Amino acids are the building blocks of proteins. Transfer RNAs (tRNAs) bring the amino acids to the ribosome. A polypeptide undergoes many modifications and folding before it becomes a functional protein.
I use special man-made RNAs called small-interfering RNA (siRNA). They are small and they interfere with the RNA, stopping the protein I am interested in being made.