Objectives

Objectives are actions or items that survivors can interact with.
Objectives vary based off of each map, but they generally fit the theme the map provides. Completing one task from an objective in Solo Monster and Double Trouble rewards the player by adding 2 coins to their counter. However, objectives in Collectathon and Strongholds need only to be touching the survivor at the given moment to be interacted with, and while they still distribute the coin bonus, it varies between the two gamemodes. The type and classification of these objectives depending on the Map or Gamemode that was chosen. Objectives are either very beneficial for the survivor team to win earlier and decrease chance of dying, or required to win depending on the Gamemode.
Objectives used to be server sided, But around the MX update (correct me if I'm wrong) they were adjusted to be client-side. Once a survivor completes every task in an objective in Solo Monster or Double Trouble, the timer decreases by a small amount, around 5-7 seconds, and your chance to become the Monster increases by 1 (as indicated by the number below your character's profile). This will only occur the first time a player completes a set of tasks, as maps with 2 objectives will not reward monster chance for completing the second set of objectives. In the two other Gamemodes, objectives are required to finish in order to win. In Collectathon, players must collect gems in order to open the exit, while in Strongholds, players must stand on control points to gain enough points to finish the round.
The way to achieve an achivement depends on the Gamemode choosen. In Solo Monster and Double Trouble, the objectives are mostly holding E on collectables until you've collected all of them to finish an objective. In Collectathon, the objective is to collect all the gems on the map and eventually escape. In Strongholds, the objective is to score points by standing on control points and achieve enough points to win. Note that both Collectathon and Strongholds are collective objectives and also required to win, unlike the two other gamemodes. Meaning that winning depends much more on other players' effectiveness.