What is the difference between the lotto and the lottery? Let's start with the definitions of both:
The lotto - A random drawing with a prize going to the winner.
The lottery - A random drawing with a prize going to the winner.
Do these definitions sound similar? Yes, actually, they are exactly the same. There actually is no difference between the lotto and the lottery.
Why, then, are there two different words for the same thing? They are synonyms. Many different words in the English language have synonyms. Synonyms are different words with the exact same meanings.
Now, depending on where in the world you live, one of the two words will be more common then the other. And, there might not even be a real reason for using one word over the other. It might just simply be how it evolved. Although lotteries have been around for thousands of years, the modern lottery, as we know it today, has only really been around for less than half a century. So, depending on where in the world you live, it will be referred to as what term was used in the last few dozen years.
In North America, including Canada and The United States, it's more common to refer to it as the lottery. No matter what game, including Powerball, Mega Millions, Cash 5, Lottario, Keno, or any game for that matter, it's often referred to as a lottery.
In other places around the world, the word lotto is more common, especially in Europe. Take Germany, for example. In Germany, the most popular game is Lotto 6aus49. In Italy, it would be SuperenaLotto. It does not matter what you call it, though, because it is the same thing, a synonym.
In some countries that refer to the game as lotto, it might even be spelled differently. Sometimes it is spelled with just one "L." Again, it doesn't matter how it is spelled because it is still the same thing.
But no matter where in the world you are, it is a game where numbers are drawn at random and the winner is the person who has a ticket that matches all of the numbers drawn. Some lotteries draw the numbers live, often on TV, while others do not. The game is usually run by the country or state and the proceeds normally go to good causes that help the community, like building schools or hospitals.