The expression "i=9" indicates that the variable i is assigned the value of 9. In programming and mathematics, variables are used to store data that can change or be manipulated. Here, i is simply a placeholder that now represents the number 9. In many programming languages, this assignment allows i to be used in calculations or functions. For example, if you were to add 1 to i, the result would be 10. This concept is fundamental in coding, where variables help manage and process information efficiently.