How to display the item that the user has selected?

On the checkbox,
type:
onClick="javascript: alert(this.value) "

OR, you may first create a function to check if the user check the checkbox or unselect it.

function XXX(what) {
if (what.checked == true) {
alert ("You have selected" + what.value);
} else {
// any action you like
}

input type="checkbox" ... onClick="XXX(this)"