Cookie Clicker was something of a phenomenon a few years ago when it originally gained traction, and it's probably still the most popular idle game today. While it wasn't the original idle game, Cookie Clicker was definitely the game that brought the genre to a mainstream audience.
As you can guess, the goal of this game is to bake as many cookies as possible. At first, you can only bake cookies by manually clicking on the large cookie to the left of the window. This is a slow and tedious process, as every click only bakes one cookie. However, once you've made enough cookies this way, you can spend them on upgrades and buildings to help make them faster. As you acquire more and more assistance, the amount of cookies baked per second grows astronomically. Eventually, the number of cookies made every second becomes pretty insane, which is entirely intentional, and seeing how high you can get the numbers to go is part of the fun.
As you can guess, the goal of this game is to bake as many cookies as possible. At first, you can only bake cookies by manually clicking on the large cookie to the left of the window. This is a slow and tedious process, as every click only bakes one cookie. However, once you've made enough cookies this way, you can spend them on upgrades and buildings to help make them faster. As you acquire more and more assistance, the amount of cookies baked per second grows astronomically. Eventually, the number of cookies made every second becomes pretty insane, which is entirely intentional, and seeing how high you can get the numbers to go is part of the fun.