Maisir is a big word that means "gambling". Gambling is when you play a game of chance, like rolling a dice or spinning a wheel, and you hope to win money or prizes.
Now, gambling can be fun and exciting, but it can also be very dangerous if you spend too much money or if you become addicted to it. That's why many religions, including Islam, encourage people to avoid gambling.
In Islam, gambling or maisir is considered haram or forbidden, just like eating pork or drinking alcohol. This is because it is believed that gambling can lead to many problems, like losing all your money, struggling with debt, or even becoming a criminal.
So, to sum up: maisir is a fancy word for gambling, and in Islam, it's something that people are encouraged to avoid because it can be harmful to your financial, emotional, and spiritual well-being.