The join() function creates a string by concatenating all of the elements in a list. The specified delimiter character separates each element in the generated string. If a delimiter character is not specified, then a blank is used as the delimiter.

result = join (list [,delimiter]);
list Required. The list whose elements are to be concatenated into a new character string.
delimiter Optional. If specified, the delimiter character is used as a separator character between list elements as they are concatenated together.

result Contains the new character string.

TrustedUsers = {"Fred", "John", "George"};
NewString = join (Trustedusers, ",");

In this example, NewString contains the character string: Fred, John, George.

For more information, please see split.