One my example of interpolated string (taken from here):

string name = "stanko";
DateTime hours = DateTime.Now;
Console.WriteLine($"Name = {name}, hours = {hours:hh}");
Console.ReadKey();

Composite string:

string name = "stanko";
Console.WriteLine("Name = {0}, hours = {1:hh}", name, DateTime.Now);
Console.ReadKey();

According to Microsoft:

Interpolated string are easier to understand than a composite format string.