Employer and Employee relationship.
1.If an employee receives salary from an employer, then the income is taxable under the head Income from Salaries.
Thus, there should be proper employer and employee relationship between payer and payee for income to be taxed under Income from Salaries.
Employee on payroll in a Company
2.If there is no such relation then income is taxable under Incomefrom othersourcesor Profitand gains of business and profession(PGBP)
Example:-Person working on contract in a Company are taxed under PGBP