What is the difference between above the line items and below the line items?

The "line" generally refers to gross profit. Above that line on the income statement,  are sales and COGS (cost of goods sold) or COS (cost of sales). Below the line are operating expenses, interest, and taxes. so the  Items listed above the line tend to vary more (in the short term) than many of those below the line, and so tend to get more managerial attention.