What is Progressive Web App ?
In simple language, A Website/Webpage which is mobile friendly and behaves like a mobile app.
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The expression "pay it forward" is used to describe the concept of asking that a good turn be repaid by having it done to others instead. In contract law, typically there are two parties but there is the concept of third party beneficiaries. Pay it forward merely applies this contract law concept so that third party beneficiary be a stranger to the creditor. More specifically, the creditor offers the debtor the option of "paying" the debt forward by lending it to a third person instead of paying it back to the original creditor. Debt and payments can be monetary or by good deeds.