Money laundering is the act of making money that came from illegal sources look like it came from legal sources. There are various laws and regulations in place to prevent money laundering. For example, there are limits to how much forex can be brought into a nation, making it difficult to transfer large sums of money out an economy through improper channels.
Money laundering is an act that lies outside the law, and it is therefore impossible to give exact estimations of how much money is laundered worldwide. However, global financial institutions such as the international monetary fund release rough estimates each year.
The process of making illegally obtained money legal is to first introduce it into an economy, to then assimilate into the economy by disguising its illegal source, and finally to integrate it into the system by investing and reinvesting it.
Each economy or nation has its own sets of laws and regulations to prevent money laundering. These include limits on how much foreign currency can be brought into or taken outside the country, as well as close inspection of money trails.