I hope u unserstood the first line.. it would return a random number from 0 - 4.
In the second line => new String[] { "a","b","c","d","e" }, is nothing but a string array it is equivalent to declaring an array and assinging it.
String[] arrayStrings = new String[] { "a","b","c","d","e" };
String name = arrayStrings[x];//this would assing the element corresponding to the random index..