My neighbour gave me a document and a cheque saying it’s a “non-judicial stamp paper” to ensure he’ll pay back the money he owes me. What exactly does this mean?

A non-judicial stamp paper is a document used for agreements and transactions that are not court-related. Your neighbour likely used it to create a legally binding promise to repay the debt. However, this doesn’t guarantee repayment; it merely provides legal grounds to enforce the agreement if necessary.