What is the method of expressing the place value of digits in a number known as?

The method of expressing the place value of digits in a number is known as Expanded Notation. This technique breaks down a number into its individual digits and demonstrates the value of each digit based on its position. For example, the number 345 can be expressed in expanded notation as 300 + 40 + 5, clearly showing how much each digit contributes to the overall value of the number. This method is particularly useful for understanding how numbers are constructed and for performing operations like addition and subtraction, as it highlights the significance of each digit's place value.