Hawala

the wikipedia goes into too much technical details.

This is a native term to me and it literally means "handing over".

You have a friend in a different city and your family member wants some immediate cash. You can wire them money, or transfer them or give a cheque and all that but you can also do one thing.

you can call your friend and tell him/her "hey. go to my family, they are in urgent need of some cash. give them the cash and i will give you the money when you come to back here or i will give that money to anyone who you tell me to give".... that's the whole hawala transaction.

the problem with governments is that this is untraceable because actually no money gets sent anywhere. This can be done from any part of the globe or city or neighbourhood.

another more sophisticated technique which is often used by unsavoury people is "you want to send money to your friend in the UK and you are in US, give me the money in US (to an agent) and the agent will give you a code. your friend in UK will go to a designated person in UK, give that code and the money will be handed over to him. no questions asked"...... This is exactly how money transfer via moneygram or westernunion or other companies work. Everyone is used to westernunion doing it but there is no track on people doing the same thing on their own.