What are symbols used for?

Answer 1

They are used for communication. For example, you are reading this answer as a sequence of 26 alphabetic characters, plus a few more for punctuation.

However, the same symbols can mean different things to different people, and in different contexts. For example, "c" is

• the first letter of the word communication, above;
• the ordinate of the intercept of a linear equation in the slope-intercept form,
• the constant of proportionality in a direct of inverse proportion,
• the constant of integration for an indefinite integral,
• the speed of light in vacuum,
• the number 100 (Roman numerals).

And, if I was writing in code, it the symbol "c" could mean something else entirely.