String objects are immutable, which means that once they are created they cannot be changed. When we use one of the methods of the String class, we create a new string object.
For example: (String strSen = “hello”; //Creates a new object).
When we concatenate any other words along with strSen variable it does not actually modify the strSen variable, instead it creates a whole new string.
For example: strSen = strSen + “Hello”, create a new string.
StringBuilder are mutable class, which means when concatenate any text to the variable it allows us to modify the original value without creating a new object.
You can use StringBuilder's Append () method to use concatenation.
