1. A nitrogenous base: This is a molecule containing nitrogen that can be either a purine (adenine (A) or guanine (G)) or a pyrimidine (cytosine (C), thymine (T) or uracil (U)).

2. A pentose sugar: This is a five-carbon sugar molecule. In DNA, the sugar is deoxyribose, while in RNA, the sugar is ribose.

3. A phosphate group: This is a group of four oxygen atoms bonded to a phosphorus atom.

These three components are linked together in a specific order: the nitrogenous base is attached to the 1' carbon of the sugar, and the phosphate group is attached to the 5' carbon of the sugar.

Here's a simple analogy: Imagine a nucleotide as a Lego block. The nitrogenous base is like the top of the block, the sugar is like the base of the block, and the phosphate group is like the studs on the side of the block. These components come together to form the basic building block of DNA and RNA.