In the most general sense, "mapping" in programming means taking several things and then somehow associating each of them with another thing.
One of the most high-level uses of this term is ORM (object-relational mapping), which means mapping rows in a relational database to objects in an OOP language, so that you can manipulate "normal" objects in your code without having to directly write SQL or worry about the structure of the database.
The programming use is also very broad, so let's start with the most concrete and well-defined meaning of "map". Namely, the higher-order map function present in most functional programming languages. Here's a trivial example of it in
Javascript:
var numbers = [1, 2, 3, 4];
var timesTwo = function(n) {
return n * 2;
}
numbers.map(timesTwo); // [2, 4, 6, 8]