Value Semantics

Copying an array will copy all of the items inside the original array.

Changing the new array will not change the original array.

var originalArray = ["Swift", "is", "great!"]
var newArray = originalArray
newArray[2] = "awesome!"
//originalArray = ["Swift", "is", "great!"]
//newArray = ["Swift", "is", "awesome!"]

Copied arrays will share the same space in memory as the original until they are changed. As a result of this there is a performance hit when the copied array is given its own space in memory as it is changed for the first time.