RNA, or ribonucleic acid, is a single-stranded molecule. It consists of four nucleobases and is found in all biological cells. The bases of RNA are: adenine (A), uracil (U), cytosine (C), or guanine (G). DNA has the same, but the uracil (U) is instead thymine (T).
Since DNA cannot leave the cell nucleus, the RNA molecule copies a segment of DNA through a process called transcription, to turn it into proteins through translation; it is called the central dogma, coined by Francis Crick in 1958.