Basic: the basic salary component. Gross: total monthly wages; do not substitute it for basic where a formula asks for basic plus allowances. Completed years: whole years of service; gratuity can apply a separate rule to a remainder over six months.
Exemption reduces income counted for tax. Threshold is the tax-free limit for your category. Rebate reduces tax after slabs. Tax deducted is money already withheld; it changes the balance, not the original liability. A refund estimate is not an approved refund.
Vesting: becoming entitled to an employer benefit under its conditions. Recognised PF: a provident fund with the relevant recognition. Approved gratuity fund: a separate approval status; a company merely calling a payment gratuity does not establish it.