This static method of the System.String class is very, very useful.

It permits you to insert values into a string, like in this sample:

cString := String.Format( "Today is {0}", DateTime.Now:ToShortDateString() )

.

You can also control the formatting:

cString := String.Format( "It is now {0:d} at {0:t}", DateTime.Now )

For more details please see the Microsoft documentation: Get started with the String.Format method