Income before tax and expenses.
For a business: total sales minus costs of what was sold.
Example: Bravedog Inc sells $400,000 of dog biscuits, spending $180,000 actually making them. Marketing and other costs and tax are $100,000. Bravedog's gross income is $220,000 and its net income is $120,000.
Gross income shows how well the business is doing as a day-to-day operation. But net income shows how good the business is overall.
For a person: salary or wages before tax and any other deductions
Example: Sam earns wages of $900. Tax and other deductions are $250. So Sam's gross income is $900 and net income is $650.