Say you sell coke, tons of coke. say you pull in 10 grand a week, but you cant just deposit it because then the SEC will investigate you. You need this money to be taxable and legit if your gonna pay rent with it.
Start a fake business!
said business will be a money laundering operation, you "wash" the dirt off the money by getting it into the sphere of "legal" enterprise, now you can go finance a new house or car with it without the SEC and feds getting in your ****. Also its taxed thus legitimizing it even more.
Good business's for this.
Resturaunts, Bakerys, Massage Parlors, Gyms, Car wash.
What you do is report the coke-money as earnings from the business, service industry is good because you can never really tell what kind of business you do.
"Yes we get a lot of cash customers, mostly simple back rubs with warm stone, and some sauna bunnies."
You report all of your drug money as income from cash-customers, with a business with little overhead, and pay a couple employees to essentially sit around.
Now all of your coke money is legitimate business money, and can be used without the tax man bringing the heat.
This is money laundering.