In the campaign mode you need to complete several missions and successfully reach the goal. There’s also a multiplayer mode where you can compete with other players online.
Clicker Heroes is an idle game focused on grinding gold to upgrade your characters. There’s no storyline in the game; in fact, it’s an endless process of beating more and more powerful enemies, progress and get better heroes. There are microtransactions in the game; however, they don’t affect your progress through the game. 
The upgrade system is set around the in-game currency called hero souls that you can use to buy so-called Ancients that buff your stats. Hero souls drop from bosses you can beat on every fifth and tenth level. The key feature of the game is the way it uses hero souls to reset the game. Every time you want to upgrade Ancients and get more bonuses, you need to use a special ability that makes you start the game over. While you need to complete the levels and develop the heroes again, Ancients’ bonuses remain and let you progress faster.
Clicker Heroes is followed by Clicker Heroes 2 that is currently in Steam Early Access. Unlike its free-to-play predecessor, the sequel uses a buy-to-play model instead of micro-transaction