It is essentially a line of credit, sort of a cross between a term and demand loan I would guess (without more details of repayment terms). Many banks have so

It is essentially a line of credit, sort of a cross between a term and demand loan I would guess (without more details of repayment terms). Many banks have something similar, only it's called "overdraft protection". Of course, as someone else has commented, with good money management, you don't need this.