C
In short
The third letter of the Latin alphabet used in English and many other languages.
In plain words
It is a symbol used to build words and sounds. It can represent a hard sound like in 'cat' or a soft sound like in 'city'.
A simple example
In the word 'cake', the letter makes a hard sound. In the word 'cell', it makes a soft sound.
Why it matters
It is a fundamental building block for writing in most Western cultures. Without it, many common words would be impossible to spell.
Easy to mix up
It is often confused with the number zero or the letter K in certain handwritten styles.