I see that you are a Nigerian. This answer from the Frequently Asked Questions on the National Lottery Regulatory Commission provides an answer to your question.
National Lottery Act 2005, defines Lottery or Lotteries to include any game, scheme, arrangement, system, plan, promotional competition or device for the distribution of prizes by lot and chance or based on the outcome of sporting events, or any other game, scheme, arrangement, system, plan, competition or device, which the president may by notice in the gazette declare to be lottery and which shall be operated according to a license. It is a game of luck involving drawing a lot for a prize. It is a strategy for fund raising for Good Causes. For example the Great Wall of China was built with funds from a lottery, the Ivy League Institutions such as Harvard and Yale were built with lottery money, the 2010 Olympics was partly funded by Camelot; the UK National Lottery. To do this, tickets are normally raised and these tickets bear different numbers and are sold to people. Numbers are then chosen on by chance and at random and whoever has the chosen numbers on their ticket wins the prize.
https://nlrc-gov.ng/faqs/Hope it is what you need.
I didn't mean the definition rather, I want a site that offers lottery maybe I can make some deposit to buy the tickets to join the raffle. Maybe if my ticket number is correct with the Winning them I will be announced as the winner, so the target is to join lottery at first I need site to purchase tickets maybe no gambling site offers lottery.