Mixed references are when either the row or column is anchored.
For example, suppose you are a farmer making a budget. You also own a feed store and sell seeds. You are going to plant corn, soybeans, and alfalfa. The spreadsheet below shows the cost per acre. The “cost per acre” = “price per pound” * “pounds of seeds per acre” – that’s what it will cost you to plant an acre.
Enter the cost per acre as =$B2 * C2 in cell D2. You are saying you want to anchor the price per pound column. Then copy that formula to the other rows in the same column: