I submitted a run for River Survival, 16min13sec, and im wondering what it means to follow a game.

Following a game helps you stay updated and informed about what's happening in a certain followed game. More specifically, when following a game you'll get notifications regarding a specific thing happening within that game, which you're able to customize.

For starters, you can only follow games (just games, not series, not users, etc.) by going to the page of that game and clicking the 'Follow' button in the sidemenu. There are several types of notifications which are specific for each game, so you can customize them separately for each game you've followed.

Once you've followed a game, a 'Follow settings' tab will appear at the bottom of the sidemenu, in which you'll be able to manage and customize which notifications you're going to receive (e.g., new fullgame WR's, new IL WR's, personal WR's being beaten, new forum threads & posts, etc.), (these settings are specific to you, and the certain game only). You can also choose to get notified through email, if you please so.

Secondly, in the settings page under 'Notifications', you'll find 'Followed games default notification settings'. These settings are the ones applied to new games followed afterwards, hence 'default'. If you want to quickly change your notification settings for all the games you're following, check the 'Apply default to all followed games' checkbox before saving your preferred settings by clicking the 'Save' button. But beware that this WILL override your customized settings for specific followed games.

Lastly, if you wish to unfollow games, you simply click the same button you followed the game at, now labeled 'Following', or manage it in the settings page.