Here's how it works:

* Nucleotides: RNA is made up of individual units called nucleotides. Each nucleotide consists of a sugar (ribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil).

* Sugar-phosphate backbone: The phosphate group of one nucleotide forms a bond with the sugar of the next nucleotide. This forms a chain of alternating sugar and phosphate groups, known as the sugar-phosphate backbone.

* Phosphodiester bond: The bond between the phosphate group and the sugar is called a phosphodiester bond. This is a strong covalent bond that holds the RNA molecule together.

So, in summary, phosphodiester bonds are the key chemical bonds that link the nucleotides of RNA together, forming the characteristic linear structure of RNA molecules.