Gimkit is similar in nature to a Quizizz, Kahoot!, Quizalize, etc - but what separates it from the others is the strategy. Participants use earned cash to purchase upgrades to use throughout the game.
Gimkit has an awesome help center - https://gimkit.crisp.help/en/ that can answer your questions, and if you do not see your question answered, you can chat with them (bottom of the help section site).
Embedded below is a 3 minute and 31 second YouTube tutorial showing the basics of the site, how to get started, what it looks like from a student point of view, etc.
More tutorials will be shared in the future. FYI - Gimkit was started by a 10th grader - Josh Feinsilber who I believe graduated in June of 2019.