Concatenation is a simple concept from linguistics, mathematics and computer science. It is a way of making a new word (or string), by joining two (or more) other strings. For example, the concatenation of "snow" and "ball" is "snowball". In most languages if we write x = "snow" + "ball", then the value of x will be "snowball". But to do the same in SQL we would write "snow"||"ball".