One very important function of nucleotides is to carry information for the cell.
This information tells the cell which proteins to make. (In turn, the proteins control how the cell behaves.)

The two nucleotides you need to know are DNA and RNA

There is only one type of DNA
DNA carries the genetic code. This tells the cell which proteins to make.

There are several types of RNA. The two most important are :

mRNA copies the code from the DNA in the nucleus and carries it to the ribosomes.

tRNA collects amino acids and joins them together to make protein.
It uses the instructions carried on the mRNA to do this.