Why shld one advertise For Free..

Advertising is a MUST for any Business..May it Be Online Or Off LINE..online advertising ..we fing free plat forms digitally..off line no such thing..but qauestion is that is it effective or just without any sustance.. Well we know there is no such thing as FREE Lunch..Then What is this advertising for free?? Is this simply an illussion and in fact nothing Free?? ver very Problematic Dear Sir There ARe effective Free advertsing Programs...letd dicuss their effec tiveness one by one ok??