Symbols are the basic building blocks of mathematics. After you have studied mathematics at advanced level for a while you will come to appreciate that certain symbols tend to mean certain things. Simple examples would be x and y, used to represent variables, or a and b used to stand for constants. The Greek symbols m and s are usually taken to represent the mean and standard deviation in Statistics. These symbols do not have to be used in this way but if everyone agrees to it then less explanation is needed. For example, the quadratic function ax²+bx+c is understood by everyone without descriptions being required of what each bit of it means.