Your income is not equal to your salary. You could earn income from several other sources other than your salary income. Your total income, according to the Income Tax Department, could be from house property, profit or loss from selling stocks or from interest on a savings account or on fixed deposits. All these numbers get added up to become your gross income.
Income from Salary: All the money you receive while rendering your job as a result of an employment contract. find all details here: https://cleartax.in/Salary#income-tax-basics
Income from House Property: Income from house property you own; property can be self-occupied or rented out.
Income from other sources: Income accrued from Fixed Deposits and Savings Account come under this head.
Income from Capital Gains: Income earned from sale of a capital asset, say mutual funds or house property.
Income from business and profession: Income/loss arising as a result of carrying on a business or profession. Freelancers income come under this head.