A tender is an offer made by a party to perform a specific act in return for removing a claim on that party. Typically, tender is money or the rendering of services.
For example, if one party owes another party money, but does not have the full amount to pay them, the violating party may offer to perform a specific act in lieu of payment.
In real estate, this may be for a party to pay a higher price for a purchase, or a borrower who pays higher fees or rates for falling delinquent on payments.