Someone who's penniless is very poor — they barely have enough money to pay for basics like food and shelter. If you're penniless, it can be tempting to buy a lottery ticket — but your odds of winning are terrible.
People who live without enough — either because they've lost a job, had other bad luck, or are experiencing a temporarily poor stage in their lives — can call themselves penniless. Some college students feel penniless, having only enough cash to buy used books for class and eating every meal in the dining hall. This early fourteenth century word comes from the sense of "without even a penny."