The difference between ROWS and RANGE is similar to the difference between the ranking functions ROW_NUMBER and RANK()

The query with ROWS sums the total_price for all rows which have their ROW_NUMBER less than or equal to the row number of the current row.

SELECT
  id,
  placed,
  total_price,
  ROW_NUMBER() OVER(ORDER BY placed),
  SUM(total_price) OVER(
    ORDER BY placed
    ROWS UNBOUNDED PRECEDING)
FROM single_order

The query with RANGE sums the total_price for all rows which have their RANK() less than or equal to the rank of the current row.

SELECT
  id,
  placed,
  total_price,
  RANK() OVER(ORDER BY placed),
  SUM(total_price) OVER(
    ORDER BY placed
    RANGE UNBOUNDED PRECEDING)
FROM single_order