well...it is the codes written by the programmer. The concept is you decalre a name for a variable, *like in maths you let a specific factor as a simple algebra x, y ,z, (like let my age be x) and you can also decalre the variable size, (like let x < / = 100) so the variable will store no more than the decalred size info. If the name (info) we typed exceed the bandwidth size of the variable set by the programmer (like i rename x = 121), the outcome name we see will be "not completed" as what dst pointed out.
*the example is a way to let you understand more but may not precisely represent the real concept of variables in codes.
**variables can not only decalred to represent numbers but also words like "String variables"