Deductions from Gross Total Income under sections 80C to 80U are intended to incentivize taxpayers and encourage certain economic activities. They reduce gross total income to arrive at total taxable income. Key deductions include those for investments/payments toward life insurance, retirement funds, tuition loans, medical expenditures, housing rent, and disability. The total deductions cannot exceed gross total income. Deductions require proof of qualifying expenditures/investments and are subject to specific limits and conditions in each section.