This figure is based on purchasing power parity (PPP), which basically suggests that prices of goods in countries tend to equate under floating exchange rates and therefore people would be able to purchase the same quantity of goods in any country for a given sum of money. That is, the notion that a dollar should buy the same amount in all countries. Hence if a poor person in a poor country living on a dollar a day moved to the U.S. with no changes to their income, they would still be living on a dollar a day.
Investing in coins and collectibles: Buffalo nickels and Spiderman comic books are good examples of coins and collectibles that can rise in value, and thus offer opportunity for passive income investors. You'll need to get up to speed on the value of any coin or collectible under consideration, but once you do so, you're on the way to price appreciation on a commodity you'll be paying a lower price to buy, and will garner a higher price when you sell.
Investor Income: This is the apex of income that one can achieve, you just have to live off your investments which you do not have to work much for once you have researched it thoroughly. Investors generate money by investing in other businesses, dividend paying equity shares, rental possessions, and other investments that need lesser amount of work. This work provides unlimited earning potential as they build their wealth as much faster rate than any other income categories.
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.